Quake 2 remastered was released at QuakeCon over the weekend. I'm very happy that I got to help a bit with id and nightdive getting it shipped.
As I mentioned on Mastodon I had a few bits of GtkRadiant support stashed away until the release. I'd like to get an updated release out, but I don't have much time right now so I've pushed the patches I have to github and zipped up the gamepack. If you have some GtkRadiant smarts you should be able to compile a working build.
The gamepack is a bit outdated, I recommend replacing the ericw-tools folder with latest. Also you may want to use TrenchBroom altogether to map instead of GtkR. TrenchBroom is easier to pickup and more active than GtkR so a better choice if you are new.
I'm being told there's a Quake Mapping discord where you can get more info about mapping for the new release. HF!