I'm sorry that you've had a hard time with your mental health, and that you're feeling disappointed with your grade
I don't have advice per se but just wanted to reassure you (as someone who also left a top 10 uni with a 2.2, due to mental health issues), that:
1) It's not the end of the world. It makes some things harder/some career paths less viable on the short-term, but it's not the end of the world
2) You've spent most (if not all?) of your degree in an unprecedented worldwide pandemic, and having lots of UCU strikes. Those two things in themselves are enough to be demotivating and give one poor mental health. So try and cut yourself some slack. Which brings me onto point 3:
3) Don't see this as indicative of your intelligence/your general ability. Poor mental health can really screw uni degrees up big time, but that doesn't make you weak, a failure, stupid, or anything like that (just saying this in case your brain is feeding you the lies that my brain fed me about my own 2.2)
Take time to process this. It'll sting for quite a while and it's important to be compassionate towards yourself