Kubuntu 20.04.4 LTS – Mount Domain Samba Shares

I have been trying to mount a simple share. All domain users should have read permissions. Kubuntu was configured for domain, I can see domain and log in with domain user. When I access shares with Dolphin file manager I can successfully open and browse them (Network -> Shared Folders (SMB) -> Add the folder).

I have tried several commands to mount this: mount -t cifs, mount.cifs, fstab + mount-a, …
All with no success. dmesg says: (I also got error -22, but idk exact setup at that time)

[ 9478.459984] CIFS: fs/cifs/connect.c: VFS: leaving cifs_get_smb_ses (xid = 330) rc = -13
[ 9478.459986] CIFS: fs/cifs/dfs_cache.c: __dfs_cache_find: search path: \DOMAIN\files
[ 9478.459989] CIFS: fs/cifs/dfs_cache.c: get_dfs_referral: get an DFS referral for \DOMAIN\files
[ 9478.459993] CIFS: fs/cifs/fscache.c: cifs_fscache_release_client_cookie: (0x0000000058c5ce4f/0x00000000c6989c97)
[ 9478.459998] CIFS: fs/cifs/connect.c: VFS: leaving mount_put_conns (xid = 329) rc = 0
[ 9478.459999] CIFS: VFS: cifs_mount failed w/return code = -13

With command, password gets accepted:

root@HOSTNAME:/mnt# sudo mount -t cifs -o username=user.name@DOMAIN '\\DOMAIN\files' /mnt/DOMAIN/X
Password for user.name@DOMAIN@\DOMAIN\files:  *****************       
mount error(22): Invalid argument
Refer to the mount.cifs(8) manual page (e.g. man mount.cifs) and kernel log messages (dmesg)

Shares are reachable:

root@HOSTNAME:~# smbclient -U user.name@DOMAIN -L \\\DOMAIN\\files                                                                                                                                          
Enter user.name@DOMAIN's password: 

        Sharename       Type      Comment
        ---------       ----      -------
        ...
        ...
        Files           Disk      
        ...
        ... 
        ... 
        ...      
SMB1 disabled -- no workgroup available

This does not work:

root@HOSTNAME:~# smbclient -k -U user.name@DOMAIN -L \\\DOMAIN\\Files
gensec_spnego_client_negTokenInit_step: gse_krb5: creating NEG_TOKEN_INIT for cifs/DOMAIN failed (next[(null)]): NT_STATUS_INVALID_PARAMETER
session setup failed: NT_STATUS_INVALID_PARAMETER

I have found some posts saying I need keyutils:

root@HOSTNAME:/mnt/4TB# apt list ---installed | grep keyutils
keyutils/focal,now 1.6-6ubuntu1 amd64 [installed]
libkeyutils1/focal,now 1.6-6ubuntu1 amd64 [installed,automatic]

fstab:

#/etc/fstab
//DOMAIN/files  /mnt/DOMAIN/X  cifs  credentials=/home/user.name@DOMAIN/.credentials/samba,file_mode=0644,dir_mode=0755,iocharset=utf8,sec=ntlmssp,vers=2.1,rw 0 0
# I have tried vers=1.0, vers=2.0, vers=2.1, no vers

Not beeing able to mount simple samba share makes me feel very silly 🙂 I hope I am doing something that is very obviously wrong.

EDIT: I have changed some stuff and got a different dmesg output:

user.name@DOMAIN@hostname:[~]$ sudo mount -a
mount error(22): Invalid argument
Refer to the mount.cifs(8) manual page (e.g. man mount.cifs) and kernel log messages (dmesg)

[86121.898379] CIFS: Attempting to mount \\DOMAIN\files
[86121.901569] CIFS: VFS: \\DOMAIN\files DFS capability contradicts DFS flag
[86121.903442] CIFS: VFS: cifs_mount failed w/return code = -22

Fstab:

//DOMAIN/files  /mnt/DOMAIN/X  cifs  credentials=/home/user.name@DOMAIN/.credentials/samba,file_mode=0644,dir_mode=0755,nounix,iocharset=utf8,sec=ntlmssp,vers=2.1,rw 0 0