I was facing this issue as well after upgrading my diskless PXE media PC, just dropped the images and saw a hanging black screen, after some boot messages read-only filesystem. Found this thread and did some research.
My debian NFS server (12/bookworm) had a (probably debian default)
RPCMOUNTDOPTS="--manage-gids"
in /etc/default/nfs-kernel-server
Removing that manage-gids (some server side permission handling according to the man pages) and adding ,vers=4.2 to the kernel boot and disk parameters as suggested above succeeded and LE 12.0.2 started up as expected.
