Really sorry that you’ve had a rough year. I hope you’re turning a corner 
I live by the line: don’t judge other people by your own expectations.
It’s helped me a lot doing this because, as an empath, I’d be knocking on your door, reaching out with a takeaway, chocolate and a box of tissues. But I also know that not all of my friends would do that.
I have a choice to have the expectations I have do (or don’t) do. Who’s right and wrong? Back to the line above, who am I or you to judge? It is their choice to be there or not, not mine.
What is your choice is to decide if their choices [of not being there], are enough for you to decide if you want them in your life anymore? Can you get past the disappointment that their actions have given you?
Do you want to call them out on how their choices have affected you?
Something to reflect up on.
As PP’s said, there could be a whole host of reasons for their actions (their own MH, pandemic, busy lives, not feeling confident in dealing with suicidal thoughts, personal issues that they need to focus on). You have to weigh up if you’re willing to except this from a friendship, or not; and if you are prepared to talk to them about it.
I’m not making excuses for them but this year (well the last 20 months) has been extremely difficult, even for those without MH history or diagnosis. People have generally struggled and got through it using every effort and “well-being” advice thrown at them. I’ve seen a lot of people power through on their own or in their own family bubble - taking on nothing but their own issues (family, work, house, life) to get through as unscathed as possible. I think friendships have suffered. It’s been almost accepted that, “you do you, and I’ll do me, and we will catch up at some point”, mentality.
Without sounding harsh, adding a more extreme version of MH to their life (suicidal) they may have though, I can’t add this to my life and bowed out of getting too close to you. It’s shit for you of course (back to the beginning of my post, I wouldn’t have - I make awesome care packages and would be on the phone to your husband to ask what I can do to support) but not all people think this way.
I like to think of this analogy - on an airplane, during the safety briefing, the words: please fit your own mask before helping others. Perhaps, just maybe, they didn't have the headspace to help you.
I hope you’re getting the professional treatment you require.
I wouldn’t stress too much about making friends. Being alone isn’t always about being lonely. Take up a hobby because you want to do it, making a friend is a bonus from it. I’ve made the most awesome friendships when I’ve least expected it. So try not to put too much pressure on yourself.