Aparrently I did not spent the time doing this before the jam - nor did I want to use Unity, Godot, or any other pre-built game engine. Instead, I used the jam as a learning opportunity to experiment with this technology and come up with this custom 3D game engine. Of course I could have made a game with a pre-made engine, but I am a bit tired (of the bloat) of today's engines and curious to learn more about making my own, so I think this was time well spent even though I did not achieve a real game - next year it should be possible to focus on that with the tech ready!
And tbh I don't think I would have come that far in getting the engine to work in just 9 days without the time pressure of the jam but yeah agree - in a perfect world I would have managed to do so anyways :D