Hi,
It helps me, when I feel this way (and I have in the past and do a little bit right now - trying to fight it) to reframe my thoughts. Instead of 'Life is so meaningless - what is the point of it all?' I remind myself life is just a free gift we've been handed and it's up to us to choose how much and what meaning to give it. The point of it all, the meaning of it all is not for us to find out, but to choose. There is a difference. Hoping to find the meaning of life can lead to utter disillusion. But deciding to choose what meaning we give it is empowering and liberating.
Right now, I'm at a hiatus because I found it easy to give meaning to life when I was raising children: they were the point. Now they are adults and really don't need me breathing down their necks advising them every second of every day. I need to find a new meaning and haven't yet. But I'm trying to enjoy looking. Meanwhile, I try to practise self-care - staying reasonably fit and healthy, keeping my home in a reasonably clean and tidy state, and trying out new things fairly often.
Can you think about anything - from any point in your life - however small (or big) that generated a positive emotion for you - a sense of joy or peace or fulfilment or self-confidence, or self-worth, or connection or flow, and excitement? Think of all the positive emotions you can, and try to recall something, anything that helped to generate them - even the tiniest flicker - like a teacher saying something nice about you at primary school, or seeing a sunset one day. Make a list of all of them and start to build activities to replicate them.
E.g. If you like wildlife, get bird feeders, put out food for foxes and squirrels, take a neighbour's dog for a walk, get a pet, save up for a holiday volunteering at a sanctuary abroad etc. Build more and more ambitious steps.
If you feel a bit better after exercise, sign up for a bootcamp or do some online classes every day, do C25K and then join a park run. From there, sign up for a longer run.
Allow yourself to accept there is no one really judges the purpose of your life except you, and it's perfectly fine to do what genuinely makes you happy. Most people find happiness comes from a sense of connection, flow and growth, so I try to focus on contributing to the world in some way, doing something absorbing and trying to get a bit better at something I'm not very good at. Would that appeal to you, OP, as a way out of the rut?