Is there a way to reduce or disable boss dungeon structure spawns? I can't seem to find a config option for this.
Since they are not spawning as structures, I also can't make them sparser via Sparse Structures.
Thank you.

They are (like vanilla dungeons) features, not structures, which makes them not super traceable. You can use a datapack to override the placed feature files https://github.com/Shadows-of-Fire/Apotheosis/tree/1.21/src/main/resources/data/apotheosis/worldgen/placed_feature to remove or lower the spawn frequencies.

Ok. Thanks