I didn’t actually have any headcanons for Adrian’s hobbies, but I do now!
Ever since he was a kid, Adrian didn’t like “passive” activities: if he didn’t have to put in thought and energy to do it, he didn’t like it. Things like TV and movies never caught his interest. When he was really young, he liked books and video games, but as he got older, he started to prefer things that had a tangible result.
It probably started when his mother began teaching him how to knit when he was five. He wasn’t particularly keen on the idea of learning how to knit, mostly on the premise that it was something that only girls did, but it actually took effort and his mother was so eager to teach him, so he agreed to it. He quickly started enjoying it, which made his mother ecstatic, which in turn made him all the more happy to do it. It became one of his go to pastimes, especially when he was stressed out or sad.
His sister also tried her best at teaching him how to sing and play the guitar/piano; unfortunately for the people listening in on the lessons, this didn’t turn out to be his forte. He loved doing musical stuff, though, so his sister could never bring herself to tell him that he sucked ass.
Also, I don’t know if this would count as a hobby, but he would constantly bring in stray animals, especially ones with minor injuries, and care for them, much to his mother’s dismay. He’d go to the library and look up as many books as possible about caring for whatever species and breed that he brought home, so he’d be an expert and give them the best treatment a 7 year old could possibly provide (I had this headcanon before the ask, unlike the other ones).
I hope that suffices. There’s not many things, but they’re pretty detailed so hopefully you’ll be happy.
Thanks for the ask! And for rekindling my love for Adrian Shephard!