I'm a bit of a serial hobbyist, so the ones that have stuck/currently (active):
* Playing the guitar - I've been playing since school, had a break to play drums but now back. I still have my 28 y/o strat but the neck is too small.
* Design and building guitars from scratch (built/play the solid body, and now building acoustic archtop - both are 7 strings with wider/deeper necks and longer scale lengths)
* Design and build tube amps / electronics - built my own guitar amp from scratch, also designed and built some audio kit and digital kit.
* koi pond (designed and built - all 14,000 litres)
* walking last one was 15 miles and that helps keep a little fitness
* snorkelling - on vacation only, but I have an ok mask, Cressi snorkel fins etc. Can easily spend hours in the water

watching the reef life like octopus etc. I'm tempted to get a nicer mask, possibly a scubapro mask, and Avanti fins in future.
* DIY - this is a love-hate relationship between dream and reality. The pond almost broke me mentally/physically and so now I limit what I can and can't do. I've laid paths, replaced fence posts etc, fitted shelves, shower with mixer, new bathroom flooring etc.
* sea fishing - this has taken a bit of a hiatus given a falling out with the mate that I used to go with (he divorced his mrs who happens to be the wife's best chum and moved away). Also the wife's dad passed away during covid and I used todo shore fishing with him. I still want to get out on a boat at some point once I'm back into employment and the fuel prices have gone back to normal..
Past
* drums
* astrophotography - not great for working and spending the night awake!
* mountain biking - this I should, I now live near the areas I used to mountain bike 20+ miles on a Sunday.
* kick boxing - got to the inter-club sparring stage, didn't want a cracked rib to stop me from working as a self employed contractor.
* hifi and repairing my kit.
* oil painting..