I saw that @brauner got a commit included into the linux kernel as of 6.15. I am running 6.17, and so should have this feature available. I assumed this would allow me to do an idmapped bind mount from inside an idmapped lxc container, however I am still getting:
mount_setattr() failed: cannot set ID-mapping: Invalid argument.
Am I misunderstanding this feature, or is there more that needs to be done to enable it?