As of 1.20.31, The custom biomes experimental feature fails to load anything from any data pack. I've downloaded, extracted and allocated the proper behaivor and resource pack files, then booted up the game, started a new world with experimental features on and the pack enabled. As soon as the world loads all of the addon content biomes/sturctures will not load. As in no new biomes and structures will be there. Its not addon specfic, its does it to all of them.

The addons ive used are (Nico's more mineshafts, Abandon ruins and structures, Beyond the underground, and The Forgotten Legends) All of which ive used before in august and know work. It only effects addons the require Custom Biomes enabled to work.