Right... Where to start!?
@NTA sorry if I've missed the ins and outs of it but your wife seems to be going through a huge amount of shit at the moment and yes ultimately its her choice to find some better coping mechanisms that mean overall family life a bit easier or manageable for her and for you. It sounds like you've tried to make suggestions to help and that's good but maybe she's so down life is just such hard work? You can't always see a way back to normality when everything is weighing you down.
I can't personally relate to the sex issue but I've known plenty of women (my age range) who have had dry spells, one admitted she'd gone up to 3 years without having sex with her husband and it baffled me but they got it back after some issues were aired. Resentment towards eachother, change of/lose of roles within their family live, betrayal, physical/mental ill health all, sorts of things that ultimately effect a relationship will effect the intimate bonds you have.
I may have missed the part where you've said this but have you asked her why? What's her reason for not wanting sex? @canefan prob applies to you too and anyone else.
A few suggestions/questions if not mentioned already...
Maybe go the other way completely. Don't be about the sex don't talk about it don't initiate etc you've gone this long try a diff approach. BUT do try to be intimate in other ways, look at your wife and smile at her for no reason, make eye contact, find subtle ways to show her you are attracted to her without being too in her face. Show her that YOU are HER MAN. Men have ways of handling women that communicate a very subtle reassuring dominance/protectiveness (and I don't mean in an oppressive way) like a really quick brief shoulder squeeze with a kiss on the forehead as you pass by or something like that. It just shows you are there, if that's not where you are at even asking if she needs a hug and you be the one to break away first so you aren't accused of being after sex. Rub her arm in passing, just reintroduce a bit of physical contact if you are at the stage of zero contact. Compliments might help too, be nice do nice things for her, not for the sex but because you want her to feel happier, the better she feels about herself the better she will feel about you and that's moving in the right direction.
You can't pour from an empty cup. And look, she knows it's shit on you, she probably doesn't act sympathetic but I bet she feels like shit knowing she's not pleasing you in that way and that will be a vicious circle of feeling shitness to get out of.
I absolutely get that you are probably feeling "why should I make the effort I'll only get pushed back" but someone has to try or you accept your lot, or you cheat (no one likes a cheat) or you split up. The fact you guys are talking about it here to a bunch of polish chicks surely means you want to try and fix it. It has to be a natural turn around though because you don't want to throw ultimatums around and her have sex with you and not want to be there (that's really shit and equally as damaging) . Sounds cliché but it's about getting the spark back and getting back to who you guys were to start with or learning about the people you are now. Unfortunately a whole lot of life happens and people can change or lose sight of things.
I'm no relationship expert, I've been a bit vocal about having a hard time during lockdown and we've struggled and have set backs most weeks but we are moving in a better direction now. And I will be honest without getting into too much detail- as bad as we've been over the last year and a half we've been pretty "active" yet intimacy has lacked at times because I've not particularly wanted sex with him- but just wanted sex, and he knew, guys know too, you shouldn't use your partner. We weren't even speaking to eachother whilst being in the same room at one point just existing together, hence huge amount of fern time, or excessive cleaning or working when I didn't need to, with the odd great sparkly day thrown in and then back to shitness.. And that was worse for me, feeling like that was going to be my life.
It always takes two no matter what the issue is, if you aren't getting something out of the relationship that you need, what aren't they getting from you? There will be something big or small. Finding out and finding a solution can help, or maybe it won't and it'll be the communication that either fixes or ends you.
Mr RL wanted more time together again just us and I'd pulled back because I'd got resentful for him previously working away a lot and that's when the damage was done and then when he started a new business which meant he was home more I was then helping him with that, changed my own work and had a child and yet he thought nothing had changed.I felt like a different person..The years just fly by but so much can happen that can change you without realising. We've both had stresses that have added to overall shittiness over the years too, his family being one of them and he also holds on to a few things from my past relationship before him and I find that really frustrating. There have been incidents of betrayal I guess you can call it on both our parts too over the years which is the shittest thing to get past. I've always had trust issues and tend to have high walls. Moving in a better direction though and that's what matters. All we did was talk talk and talk when we got to a particularly explosive point because that was all we could do in the end. And now we keep that communication open.
Some people have mentioned counselling etc above but I would have hated that with a passion but then it may have got us speaking sooner?
Happiness scale for me I probably couldn't share,I try and find something to be happy about everyday but my life isn't where I thought it would be or hoped it would be and I've lived with a feeling of being bit incomplete or lost for most of my life - man that sounds depressing and I really don't mean it like that, I have reasons I wouldn't go into on here. My daughter has helped me sort of let go of a few things I felt I should have done or I've given myself permission to move on from goals I'd set myself etc,i guess when you have your own child it puts things into perspective but opens another can of worms in other ways.
Guys I hope you get laid soon, I mean that most sincerely. 
(also credit to King Henry 8th)