Upstream has released updates that appears to apply and compile correctly.
This update has not been tested by PaperMC and as with ANY update, please do your own testing
Bukkit Changes:
f47abd88 SPIGOT-6242: Fix some file line endings
de96535b SPIGOT-6234: enum classes don't serialize properly when implementing ConfigurationSerializable
CraftBukkit Changes:
4475707d SPIGOT-6244: /spawnpoint ignores angle
8b3b096d SPIGOT-6242: Fix some file line endings
4b33c749 SPIGOT-6186: Canceling a CreatureSpawnEvent results in a "Unable to summon entity due to duplicate UUIDs" error
2b3ca726 SPIGOT-6236: Vehicle passenger portal cooldown does not change
When new advancements are added via the UnsafeValues#loadAdvancement
API, it triggers a full datapack reload when this is not necessary. The
advancement is already loaded directly into the advancement registry,
and the point of saving the advancement to the Bukkit datapack seems to
be for persistence. By removing the call to reload datapacks when an
advancement is loaded, the client no longer completely freezes up when
adding a new advancement.
To ensure the client still receives the updated advancement data, we
manually reload the advancement data for all players, which
normally takes place as a part of the datapack reloading.