It’s a toss up between cooking and home networking for me.
Cooking because it started off as just finding neat recipes and giving them a shot to now experimenting with new techniques and harder to procure ingredients. My pantry looks like a mini spice market and keeping them fresh is its own hassle. Plus needing all the gear gets expensive!
I also got really into home networking during the start of the pandemic. I went from having a simple off the shelf mesh network to a full network rack in my basement serving some high end access points and cat6 drops in every room. Now I have a pretty secure iot stack that’s separate from my main vlan and one devoted to my work computer.