We are a two person team and we have used UE in the past. Our first game for game jam was on Unreal Engine, but it lacks good web support so we decided to try to create our own little "engine" on C++ to participate in game jams and maybe eventually be able to create larger games for Steam. We are only using some small libraries like sokol, jolt, raudio, entt.
So far our engine does not even have GUI and we are basically just using Blender for level design loading a whole game with one gltf file.
Our game for this jam is: https://nesobaka.itch.io/fragments
Two last games are also created using our engine for other game jams in this month