Hey I made a website with books full of go problems. It's become quite popular: https://tsumego.tasuki.org/
It's non-interactive not just because I'm lazy, but also there's some reasoning for why you should solve problems rather than click around and randomly try things out :)
Thanks for your site! I've been there before. I really like the Cho problems.
Cho Chikun is the popular one. My favourite is Gokyo Shumyo!
There's also books and sites with "go problems", chosen puzzle positions, for a quick fix (but only after you know the game a bit).