Or is it really rude to make your food preferences known if you aren't the host?

I have an eating condition called afrid. Certain textures make me gag, I can eat quite a lot of foods. But somethings I would literally repel back on to the plate. I have issues around dates on condiments/sauces. How long things have been open. How food is stored. How things are cooked.

Needless to say I don't eat out much. But I actually find it extremely rude that a person would prefer their guests to be unhappy rather than have the opportunity to make them something they enjoy.

If its not allergies/intolerance then I think I could cope with 1-2 items someone cannot stand. I say this because I have some items I absolutely cannot eat, I almost have a fear of them. I'm not allergic or intolerant. But I can't. So it's pointless making anything with it in.l and expecting me to eat it.

If I was the host I would say something like "I'm thinking of cooking lasagne - are you all ok with that?".
I would definitely check with them if there's food they don't like before buying anything.
Why would you invite people round to feed them food they don't like?

A lot of people have aversion to seafood so I think you were a bit silly not to check with your guests

Whenever we invite people round for food I always ask them to let me know what to avoid.

That is good manners as a host.

Why would you not do that @UnlikelySuperstar?

You have reminded me of the hideous occasion a guest told me that they and their partner were:

Gluten-free - OK
Vegan - OK but now a bit more tricky
Allergic to all spices - WTF!

We don't see them at our house any more and make them pick the restaurant.

That is shockingly rude OP! Allergies aside, they are displaying very poor manners.

I think it depends. Telling your host in advance that you'd like fillet steak because chilli con carne is beneath you is absurdly rude.

Telling someone that you don't eat smoked fish because it makes you physically sick is not. It's only sensible to tell your host because no-one wants vomit on new cream carpet.

If I don’t know what people like, as a host I’d always ask. I’d hate someone to feel they had to choke down food on my account.

It would depend. If someone wasn't fussy and really didn't like a specific food then I'd appreciate the heads up that they really don't like it. I'd rather not make something with fish if someone really didn't like fish. It's no big deal to me.

If someone handed me a list of all the items the don't like /would rather not eat then I'd find it rude though. It makes catering difficult and to me it's quite self-absorbed of the fussy eater to do that.

If I was hosting I would always ask my guests what their likes / dislikes were.

I'd rather know but I'd rather know well in advance. I'd take it that they are close enough friends that they felt ok telling you.

Hhmm? I don't know really. Was it an extensive list?
Some things you just can't pick around. I'm not allergic, but I really can't handle chilli and spicy food. I always let hosts know this and most try, but it amazing how many people say...oooh, it's not that spicy, you should be ok 🙄
I'm not going to eat spicy food to keep a host happy and If I was hosting I'd make sure all my guests had plenty to eat they liked.

Presenting you with a list late in the day is rude and strange, but I do always ask if I'm hosting if there's anything my guest really doesn't like, and double check specifically if I'm using any particularly controversial ingredients like coriander. I wouldn't want them to be sitting there uncomfortable and pretending to enjoy it out of politeness!

Very rude.

I remember being told very clearly by my DM as a very picky child that if I was at someone else's house I ate what I was given, pretended I liked it and thanked the person making it.

Not always easy to do was nearly sick at MIL's but a good rule for being a guest

I don't really like seafood I'd hate to go to someone's house and be served calamari or mussels you would be offended if i picked at it or just couldn't eat it, wouldn't you rather know dislikes than someone not eating or enjoying your food?

I suppose it depends how it’s done. I don’t like seafood in any form (really wish I did!) and couldn’t even force it down! I’d hate you to waste your money on me so I’d politely find a way to let you know I don’t eat seafood and if that was an issue due to your planned menu, I’d happily bow out of that course or the dinner party altogether etc.
Personally, if I was throwing a dinner party, I’d ask my guests if there was anything they had a particular dislike of. Just saves the hassle all round!
Certainly wouldn’t act like your description of your YABU though! If I hadn’t told you in advance, I’d either not eat that part or eat around if possible

If someone lets me know in advance that they can’t stand tomatoes/mushrooms/tripe then I’m fine with that. I’d far rather cook people food they actually want to eat than forcing down stuff food on principle that makes them feel sick.

But a last minute request? You’ll get what you’re given.

If you have so many food aversions you can't get through a meal at a friend's then you don't go. Or you invite everyone to yours.

I love my friends and I'd hate to think I was virtually forcing them to eat something they hated, just to appease me.

That said, if I was inviting them to dinner I'd run the menu past them before shopping anyway.

I would hope someone would tell me if there was something they really didn't like. But long enough in advance that I hadn't already bought it by the time they told me!
Personally, I wouldn't say anything as a guest and would just make the best on the day.