As an update to this, this appears to be on track for Ubuntu 24.04 still, as per Bug #2046844 “AppArmor user namespace creation restrictions caus...” : Bugs : apparmor package : Ubuntu which is tracking package level fixes going into the Ubuntu repositories.
Ubuntu 22.04 won't offer an upgrade to 24.04 until July (alongside 24.04.1), but there could possibly be a rise in bug reports relating to this from people who have done the upgrade from a previous version of Ubuntu but haven't re-run the installation script since.