NFS automounts failing to mount using Big Sur, says "unable to mount with current lock mode"?

Hello everyone! Yesterday, I upgraded to Big Sur.

After the upgrade, I checked my auto_master (okay!) and auto_nas (also okay!) files to insure they made it - and they did, but for some reason I can't figure out, I cannot automount remote NFS shares.

When I try to cd into the automounted directory, which worked fine in Catalina:

[etimberl:/System/Volumes/Data/nas] 1 % cd pictures
cd: rPC prog. not avail: pictures
[etimberl:/System/Volumes/Data/nas] 1 %

... I get the following on the console:

error	19:44:18.582549-0800	backupd	Failed to read capabilities for 'file:///System/Volumes/Data/nas/pictures/', error: RPC prog. not avail
default	19:44:18.606887-0800	kernel	nfs: STAT(NSM) rpc service is not available, unable to mount with current lock mode.
error	19:44:18.611119-0800	backupd	Failed to read capabilities for 'file:///System/Volumes/Data/nas/musicvideo/', error: RPC prog. not avail

When I make a few queries from the command line, all APPEARS to be working:

Soooo... The changes to NFS mounts in Catalina were reasonable easy to find and update, but all I can find so far are LOTS of other folks having issues with previously working NFS setups, but no actual fix can be found be yours truly so far.

Thinking it could be an obscure firewall issue, I disabled it, but there was no change in behavior.

Any ideas? No changes to the NFS server, which is working for all other clients just fine, just not this Big Sur based system, which itself worked just fine two days ago under Catalina..

HELP??