AIBU to struggle with having to hide my genuine opinions about colleagues at work?

Can't you just get your head down, do your job and go home? Presumably you've got friends outside work that you socialise with so don't need new friends.

Pretending to be interesting and asking "how was your week-end" etc is par for the course in the work environment unfortunately, so yes, you are expected to do this a bit. If exchanging bland pleasantries isn't for you then perhaps office working with a team isn't for you either. Have you considered going self employed?

Why can’t you tell her to simply stop commenting on your desk and zone out and ignore her when she talks about designer stuff?

For the messy desk thing it is ok to say "I find it rude when you make those remarks, please don't".

For the bags thing, in the past I have said "wow that's a whole month's rent for a lot of people!" like in a tone of value neutral wonderment and it shuts them up.

She won't love you for either but then you don't like her anyway.

Very few people bring their authentic self to work.

most people have at least one colleague that they don’t get on with.

being professional - maintaining working relationship without telling them you hate them.

if you hate all of them look for a new job.

She finds you messy, you find her materialistic. Live and let live. Do your job and go home. Polite is fine.

The way to manage this is to tell her her comments are upsetting you and making you sad (e.g.. when she comment on your desk).

This way it puts the onus on her to manage her behaviour.

And yes, NT do not bring their “authentic self’ to work. I filter what I say ALL THE TIME!

It's not the same, because OP is not making comments to this woman but this women is commenting to OP.

Pretending it's equal doesn't help the OP, does it?

AIBU to find this aspect of working life so frustrating? And what practical strategies would you recommend?

Keep your head down and get on with your job.

Stop overthinking.

Remember it's possible that she really dislikes you too.

I'm not autistic but I do find lots of people annoying and don't much enjoy small talk with them. But I frame it as a requirement of my job: part of what I'm being paid for is having good working relationships. So that means it's my job roll to nod and say blandly, "that's interesting."

There are some relationships for which honesty and authenticity are key - like romantic partners. There are some where civility is more important. Would it help you to categorize people and connections into one or the other?

That said, I would have some ready phrases you can default to:
"Sorry I can't chat now, I'm on a deadline"
"I don't really know much about x"
"Oh, I'm not the person to ask about handbags/whatever"
Which is to say, you don't have to pretend to be interested. It's not a split being feigning loads of interest Vs being rude - you're trying to convey polite uninterest, in the way you might decline a food item you don't like: "not for me, thanks."

Your "authentic self" sounds pretty judgemental TBH.

Most people find this hard, I think.

I've never found a solution -- other than to remember that I am being paid for being there, and part of the job I'm paid for is to perform an appropriate work persona.

I’m in the same boat OP but I think you just have to get on with it. Some people can be very annoying though I think it helps to bear in mind that others may find us annoying too. Personally I have never felt any need to be friendly with work colleagues unless we genuinely are friends. But it is extremely important to be respectful and polite and professional in working relationships, how would team working and collaboration be possible otherwise? So I do pass a minute or two every morning chatting to my verbally incontinent work neighbour though I don’t give two hoots about her pets or tv viewing habits. I help a few people on the team with various work issues throughout the day as being 59 I’ve seen most of it before and so can. It’s just a necessary part of working life and I figure that doing all this helps me continue to receive a salary. I rarely dislike people though, I just view them as different. Practically I take regular short breaks from the team, walking round the office (which is huge) a few times a day and always taking a longer break at lunchtime, when I leave the office for a walk or meet friends. Over my career I have once moved teams to avoid a person, though I said I was looking for a sideways move to further my experience. I’ve also been honest and asked to move desks to avoid sitting next to someone who wore strong perfume that gave me headaches, but that was OK because at the time I had a manager I trusted. So I suppose what I’m saying is be strategic and adopt clear ways to make office life comfortable for you.

Op cannot police what this other woman talks about at work. Including her “messy desk”. She can ask her not to comment but she can’t force her. That is life.

Yes but your advice of 'live and let live' is for OP to be a doormat and not say anything.

My autistic DD has adopted the phrase, "you fo you, hun". It's about finding ways to either change the subject or zone out. You can state that you aren't interested in handbags. Then talk about something that you do like. You don't have to put up with being talked at.
You just tell her your desk suits you. I just get people talking about themselves, do they celebrate Halloween/Christmas etc. NTs fake it as well.

lol! Doormat? No. And OP is hardly a doormat, she appears to have many judgmental opinions of said colleague. Accepting that you won’t like all your colleagues and that they won’t like you, but being blandly polite, isn’t being a doormat, in any way.

1. How do you work alongside people you genuinely dislike without feeling you're constantly pretending?

You have to be comfortable with the idea it's OK not to like everyone you work with, but it's not OK to be unprofessional. Other human beings, whether you like them or not, are deserving of civility and courtesy unless they themselves breach that rule. So you tell yourself you are displaying the same civility and courtesy to a colleague by being pleasant, that you would display to a stranger you'd never met.

1. Is it acceptable to be polite but emotionally distant, rather than friendly?

'Friendly' and 'emotionally distant' aren't mutually exclusive. You can make pleasant conversation without getting emotionally involved. If they're showing off expensive purchases or whatever, just nod and say something neutral such as 'I'm glad you found a bag you liked' or if there is something you genuinely admire about it, you can say so such as 'that's a nice colour' or 'that's a handy size for work'.

1. How do you set boundaries with colleagues who irritate you without creating conflict?

Best to indicate you have things to get on with, in a conversation closing sort of tone. "Right, I need to get my head down now." "Best get on now, I've got lots to do this afternoon"

1. How do other autistic people cope with the expectation to filter their genuine opinions at work?

I will try to explain it like this. Have you ever seen a film where someone is e.g. given a truth serum or there is some other reason why it's impossible to lie? Usually for comic effect. E.g. Liar Liar, The Invention of Lying? Those films always slightly irritate me because they mistake the concept of being unable to lie for the concept of being forced to blurt out every random thought that comes into your head. They ignore the fact that saying nothing is not 'lying'. That's how you filter your opinions - if the opinion is likely to cause offence, don't air it,

1. How do you distinguish between being authentic and being unnecessarily blunt?

Despite many workplaces blithely saying they want you to be 'authentic' - actually they don't. If everyone was authentic - and I include neurotypical people in 'everyone' it would create absolute chaos. Don't say things unnecessarily that are likely to cause offence or distress - I don't mean that you should avoid difficult work-related conversations, sometimes if it is work-related it's better to be direct - I'm talking about social interactions. "If you haven't got anything pleasant to say, stay quiet' is a good rule socially, also "Don't get involved" when it comes to gossip or potentially loaded conversations about politics, sex, money - that kind of thing.

To be fair if the OP was going to say anything she would have, rather than starting these threads.

My DH is autistic and frequently tells me how painful he finds it that nobody knows how much he despises them, and how unfair and exhausting it is that he’s expected to work so hard to spare them the knowledge of his deep dislike.

He doesn’t believe me when I tell him that most people don’t go around all the time boiling over with intolerable loathing for the people around us.

He thinks people who manage to be polite and friendly are liars and hypocrites, and that his burning desire to let people know how much he dislikes him makes him a better quality of person with greater integrity.

He will not contemplate the possibility that other people might not go through life as he does, utterly wracked with rage about the presence on earth of others who might not agree with him about everything, share his exact opinions and interests, and celebrate his messiness and squalor for the evidence of high intelligence and creativity he knows it to be.

I find this an unpleasant worldview, and fairly exhausting and depressing to be around.

I don’t know what you do about it, if you dislike everyone to this extent and it pains you so much not to tell people.

You don’t need to bring anything more than inane good manners. You don’t need to be your ‘authentic self’. I know it’s exhausting (I’m neurodiverse myself), but it’s a part of working life. If you’re really struggling then of course you could look for something else, but now isn’t a great time to be doing that and, besides, there’s going to be an element of this everywhere you go. Your other option is just to say what you think, but you’re likely to be regarded as hostile and antagonistic, which is also going to be an exhausting thing for you to deal with.

It certainly does!

This is so useful, it should be handed to every new recruit and pinned up in every office kitchen 🙏

What would it benefit you, or your colleagues, for them to know you deeply dislike them? Part of life is being able to get along with people you might not choose to associate with but need to for whatever reason. That does mean not being your “authentic” self, because for most people that would lead to really unpleasant behaviour at times. It’s an important life skill to be able to make enough small talk to ease communication and collaboration at work. You don’t need to be emotionally invested in her handbags, and you can roll your eyes when she comments about your mess, maybe consider there are things she doesn’t say to you because they would be hurtful or unprofessional.

You bring your professional self to work, your authentic self is for friends and family.

Your employer is not only paying you for your time, skills, experience and output but also for your professionalism.
Not everyone will like everyone they work with but we are required as part of employment requirements to remain professional and polite. That’s how it works. It’s that simple really.