Strongholds appear to not be generating – using the /locate command turns up the "Could not find that structure nearby" error, and Eyes of Ender don't work when thrown. Comparing seeds between the most recent Experimental Snapshot and 21w37a, strongholds are not appearing in 21w37a where they did in Experimental Snapshot 8. All other overworld structures (including those that do not work with /locate, like Dungeons and Geodes, appear to be generating successfully, so it appears to only be an issue with strongholds specifically.