Comment 20 for bug 1680224

I commented in the MP, but let me add something here too.

Groovy/focal with autofs 5.1.6-2 (same package as debian) show the same problem. And the packages from the attached MP for bionic still won't work:
Jun 1 20:05:15 bionic-autofs kernel: [ 751.949808] CIFS VFS: BAD_NETWORK_NAME: \\bionic-autofs\C$dollar

I don't think that "dollar" was meant to be literal. Actually, it doesn't look like any escaping is needed:

root@bionic-autofs:~# mkdir /manual-cifs
root@bionic-autofs:~# mount -t cifs //bionic-autofs/C$ /manual-cifs -o user=ubuntu
Password for ubuntu@//bionic-autofs/C$: ******
root@bionic-autofs:~# l /manual-cifs/
this-is-c.txt*

and

root@bionic-autofs:~# umount /manual-cifs
root@bionic-autofs:~# mount -t cifs //bionic-autofs/C\$ /manual-cifs -o user=ubuntu
Password for ubuntu@//bionic-autofs/C$: ******
root@bionic-autofs:~# l /manual-cifs/
this-is-c.txt*

But C\\$ won't work:
root@bionic-autofs:~# mount -t cifs //bionic-autofs/C\\$ /manual-cifs -o user=ubuntu
Password for ubuntu@//bionic-autofs/C$: ******
mount error(2): No such file or directory
Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)
root@bionic-autofs:~#

By removing the $ gsub() handling in auto.smb, it works:

root@focal-autofs:~# /etc/auto.smb focal-autofs
awk: cmd. line:9: warning: regexp escape sequence `\&' is not a known regexp operator
-fstype=cifs,uid=$UID,gid=$GID,credentials=/etc/creds/focal-autofs \
         "/print$" "://focal-autofs/print$" \
         "/myshare" "://focal-autofs/myshare" \
         "/C$" "://focal-autofs/C$"

root@focal-autofs:~# l /cifs/focal-autofs
'C$'/ myshare/ 'print$'/
root@focal-autofs:~# l /cifs/focal-autofs/C\$/ <--- even used tab complete here
this-is-c.txt*
root@focal-autofs:~#

Also works without tab-completion:
root@focal-autofs:~# systemctl restart autofs
root@focal-autofs:~# l /cifs/focal-autofs
'C$'/ myshare/ 'print$'/
root@focal-autofs:~# l /cifs/focal-autofs/C$
this-is-c.txt*
root@focal-autofs:~#

Maybe it's time to confirm with upstream, since groovy has the same issue still and is the latest version?