Ramblers' Association is nationwide. All age groups, but mainly older people. Excellent exercise, days out and new places/friends.
You are obviously computer literate - my local college does very cheap courses in IT, from word processing to web design. You'd all have a common interest and be able to exchange skills / tips.
How about a totally new skill that you've never tried? See what evening classes are available to you - cake making, car maintenance, learn a language. Something different to how you see yourself.
I think I already suggested voluntary work - nothing too taxing. Perhaps a few hours in a local charity shop.
I wish you all the best.