OK, Samba issue resolved by:
- as @fzinken recommended in the thread: Samba is not working - #25 by Fye , replace the smb.conf with new distribution version after update.
- partially restore the config, but cross-check with samba new manuals as options like “security = share” cause samba to crash
- (optional) bind only to specific interfaces to avoid mentioned wifi problem (1).
- re-add and re-enable cifs users with smbpasswd
- add “ntlm auth = yes” to smb.conf to keep old behavior
The rest (1) and (3) still broken, unfortunately.
apt-get update and dist-upgrade double-checked, nothing to update, no issue.