Personally, the only extension I really care about is the MJ2 extension, but there are others, and none of them are built, or have USE flags to enable the possibility to build them.
cmake options to enable the available extensions are documented here:
I'm aware of them but didn't have time to test & include them due to rushing for the security bug that was the main concern.
Thanks for opening this bug as reminder. Will try to get them soon.