Also, https://puzz.link/db/

You'll have to find the puzzles' rules by yourself tho.

There is a Help->Rules link on all of the puzzles linked here. It can be a little tricky to decipher them if you're coming to them completely brand new, however. I mostly use them as a refresher.

You're right, but not all of them link to the puzz.link player. The ones using the pzv.jp player, for instance, lack that feature.