According to many of your previous posts you like
animals.
How about doing shit with them/for them? Like keeping them or simply helping at a shelter.
It's never too late to acquire some knowledge there and learning can be quite fulfilling when it comes to animals. They improve the life quality of many individuals by providing companionship/love and give a life purpose via regular responsibilities.
Even doing research about them on the Internet is fun. For most animals there are nowadays excellent care sheets available and many of the invertebrates (or even some reptiles/fish/amphibians) require little care/cost/maintenance/attention and many easy to keep/breed species can be bought there for little money.
Of course for forming real bonds/touching mammals are the better alternative, although many reptiles/amphibians/fish recognize (or seem to recognize) you too (or at least associate you with food). And via animals you can form irl connections with many enthusiasts/other good people.
Gardenmaxxing is fun too, there are nowadays many apps to help with the start (for example for identification), there are guides everywhere on how to keep different plants and many interest groups where you can connect with more experienced keepers. It's the same as with animals albeit with far less responsibilities/guilt when something goes wrong.
Don't listen to guys that tell you that you need to be young to learn a completely new trade/skill set, I know many guys who became complete lateral entrants even in their 30s/40s and are now considered to be experts about that field.
[UWSL]This applies to all trades/skills too, [/UWSL]
it's of course easier to learn it when you are younger but it's never too late[UWSL], neuroplasticity decreases by a small amount with age, but nothing too drastic. My pulmonogist was once a carpenter until switching, one of my fav animal experts was once a salesman, etc. This is the problem with that forum: People overexaggerate truths. Flexibility indeed decreases with age, but that doesn't mean that it's impossible to do something new.[/UWSL]
Furthermore, fuck doing productive things, if you just want to rot/LDAR while
listening to music/playing vidya/foodcoping nobody can blame you.
Reading something can be fun too, with libgen or z-lib you can get gratis access to many books (both scientific and popular literature).
Other good copes would be Discord simply for hearing the voice of another human being. Political discords (particularly for fringe politics) contain many people in similiar situations.
I also watch documentaries often when feeling down, particularly about WWII/other shit.