Upgrading to Big Sur caused the same problem for me. I had a samba share on a Linux server working with Catalina (Fedora 33 sharing an ext4 filesystem). To get it going agin, in /etc/smb.conf, explicitly disabling the 'fruit:nfs_aces' global option got my backups going again: fruit:nfs_aces = no
Topic:
App & System Services
SubTopic:
Core OS
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