As someone with self-diagnosed mild depression and probably adhd, I've struggled with this.

Lots of people have suggested running or walking, can confirm, that does help. I would also add music to that. Throw on headphones, start your favorite playlist, crank it up good and loud, and go for a walk/jog/run. No one is watching you, no one is judging you. Silently lip sync sing with the songs as expressively awesome as you can (or sing out loud for real if you can, but I know this would be hard for me, for whatever reason I'm much less self conscious about my ridiculous facial gymnastics as long as I'm quiet about it). Like for real, pretend this is your song, and you're performing it live at your band's concert. Entertain the shit out of your imaginary audience. Belt it out like there's no tomorrow. To quote Straylight Run's "Existentialism on Prom Night," sing like you think no one's listening. Combined with the physical activity, you'll feel great when you get back home. For even better effect, find a bunch of songs where the tempo matches your walking speed. Then you can really get into a groove with it.

I also go on walks with my wife most evenings now, no music/headphones, just kinda small talk and enjoying each other's company, and it's helped get some things back on track with our marriage too. Better communication. Not both of us sitting on the couch silently doomscrolling and ignoring each other.

I can also suggest 3d printing as another good hobby, though this one will cost you, so it comes with the caveat that you'll probably want to have at least a bit of discretionary income if you want to pick this one up. There are tons of free, ready-made models on sites like thingiverse.com, thangs.com, or printables.com. Public libraries sometimes have 3d printers available for public use, and any makerspace worth their salt will have some too, if you're in an area that has something like that. So you can piddle around with it a bit before you really start laying out cash, see if it's something you'll like.

Start small, find a dinky little trinket or toy or something that can be printed quickly, and watch that mfer come into existence layer by layer. It's addicting. When the print bed slides out at the end with a physical object that didn't exist an hour ago, it's kind of fantastic.

Once you decide that you like it, you'll want to get a printer of your very own. You can find very hands-on tinkery printers (creality ender 3 series) for $100 and up, if you're good getting your hands dirty and buying more parts to "fix" some of the entry-level shortcomings. Good, ready-made "as good as your gonna get" options from Prusa or Bambu are higher priced initially ($500+) but won't require nearly as much extra money for upgrades and tweaks. Filament usually costs about $20-30/roll depending on how fancy you want. You can do toys. You can do lithophanes (cool 3d printed photographs). You can print replacement parts for random shit in your house that breaks. Guns. Action figures. You can print an entire fucking life sized Tyrannosaurus Rex skeleton (Reddit link, warning to anyone who's avoiding the old site). And all the while, you'll need to read and research and tweak and change and do all kinds of little mental tasks to engage yourself and pull out of your funk.

Your thing will fail sometimes. You'll run out of filament. Your settings will be wrong. You'll end up with a big blob of plastic spaghetti. But that gives you incentive to find and fix what went wrong and try again. It'll come out right eventually, and it feels great when it does.

Once you've gotten your feet wet with models from the Internet, you can get into starting to learn modeling yourself, with Blender or FreeCAD or any number of other apps. And if you thought it felt good when your cheesy little boat or octopus from the Internet finished, let me tell you... When your own model, that you created from absolutely nothing, comes off the printer as a real honest-to-god physical object, looking exactly like it did in your head, it's sublime!

Anyway. Good luck to you. Good on you for reaching out and looking for ways to improve yourself. I hope you find something that works for you.