I have started upgrading our systems to RHEL 8.5 (actually AlmaLinux 8.5), which was just recently released. After the upgrade, the nodes cannot rejoin the cluster. I spent about an hour searching on log entries until I found the issue below.
Apparently the fix is due in XtraDB 8.0.25, which has not yet been released. So, your choices are a) do not upgrade to RHEL 8.5 until the new version or a fix for XtraDB has been released or b) manually patch/edit the /usr/bin/wsrep_sst_xtrabackup-v2 file with the following changes.
Hope this saves someone else some time. Wish I had known before I upgraded.