Stumbled across this: GitHub - apistol78/traktor: Traktor Game Engine · GitHub
Made by the now-dormant, two-person Swedish development studio Doctor Entertainment who have since open sourced their engine. Seems to be actively maintained by their solo engine developer, who is making some kart racer in it as a hobby project / engine demo, but otherwise their last shipped commercial game as a studio was 10 years ago. There’s a Discord, but I haven’t checked it out so dunno whether there’s much of a community there. I suspect this may resemble many of the projects you’ve investigated in this thread.