I had some success loading and activating game feature plugins using Hotpatcher. GitHub - hxhb/HotPatcher: Unreal Engine hot update manage and package plugin. and the GFP paker for it GitHub - hxhb/GameFeaturePacker: Unreal Engine Plugin/GameFeature Packager Mod.
Unfortunately support stopped at 5.2, but I confirmed it works. I even had it working on the quest loading blueprints, static meshes and new materials. Maybe others can learn from this project, how its activating the GFPs.
I really liked being able to activate game feature plugins from paks at runtime. The modularity of adding new content and game mechanics via paks seems incredibly powerful.