There is some discussion around on Slipseer (a newish Quake 1 forum), about including a section for Q2 modding. It is not active yet, but it may be interesting once it is added.
https://www.slipseer.com/index.php?threads/quake-2-support-yay-or-nay.129/
Additionally, I have found some stuff on moddb including the following compilation of early maps.
https://www.moddb.com/games/quake-2/addons/quake2-superpack-1
https://www.moddb.com/games/quake-2/addons/quake-2-super-pack-2