[Samba] Samba mount error after server packages update

[andycapo at virgilio.it]

Hello,
I've a virtual machine working as a samba server ("clear linux release 28640", whose relevant information are in the attached file "server_clearmi_28640.txt").

The samba client is an android 4 virtual machine (https://www.android-x86.org/releases/releasenote-4-4-r5.html).
I can succesfully mount samba shares from the android "terminal emulator", with the following command, for example:
---
# android_share
su root busybox mount -v -t cifs \
-o username=andy,password=pass,nounix,nosuid,nodev,noexec,noatime,gid=10028,uid=10023,rw \
//192.168.213.133/android_share /sdcard/android_share
---
So far so good.

Now I have just upgraded the server machine to "clear linux release 33490". Only the full system upgrade has been performed, with no other changes.
After the upgrade, the samba version has been updated from 4.10.0 to 4.12.3.
The samba server starts correctly (and it works correctly with windows clients), but when I try to mount the filesystem on the android client (with the same command shown before), I get the following error:
"operation not supported on transport endpoint".

I don't understand if this is a bug in the new server, or if the updated samba release requires different parameters in the smb.conf file.
Any suggestion?
Andy
-------------- next part --------------
andy at clearmi ~ $ swupd info
Installed version: 28640
Version URL:       https://cdn.download.clearlinux.org/update/
Content URL:       https://cdn.download.clearlinux.org/update/
andy at clearmi ~ $ uname -r
5.0.6-726.native
andy at clearmi ~ $ sudo smbstatus

Samba version 4.10.0
PID     Username     Group        Machine                                   Protocol Version  Encryption           Signing
----------------------------------------------------------------------------------------------------------------------------------------
514     andy      users        192.168.213.1 (ipv4:192.168.213.1:55925)  SMB3_11           -                    partial(AES-128-CMAC)
620     andy      users        192.168.213.135 (ipv4:192.168.213.135:40103) NT1               -                    -

Service      pid     Machine       Connected at                     Encryption   Signing
---------------------------------------------------------------------------------------------
android_share 620     192.168.213.135 Wed Jul 15 11:34:54 AM 2020 UTC  -            -
andy      514     192.168.213.1 Wed Jul 15 11:10:06 AM 2020 UTC  -            -

Locked files:
Pid          Uid        DenyMode   Access      R/W        Oplock           SharePath   Name   Time
--------------------------------------------------------------------------------------------------
620          1000       DENY_NONE  0x120089    RDONLY     NONE             /home/andy/android_share   archive1.rar   Wed Jul 15 15:38:41 2020
620          1000       DENY_NONE  0x120089    RDONLY     NONE             /home/andy/android_share   archive1.rar   Wed Jul 15 15:38:41 2020
620          1000       DENY_NONE  0x120089    RDONLY     EXCLUSIVE        /home/andy/android_share   archive2.rar   Wed Jul 15 15:38:41 2020
514          1000       DENY_NONE  0x100081    RDONLY     NONE             /home/andy   .   Wed Jul 15 11:28:49 2020

andy at clearmi ~ $ cat /etc/samba/smb.conf
[global]
    workgroup = WORKGROUP
    passdb backend = tdbsam
    printing = cups
    printcap name = cups
    printcap cache time = 750
    cups options = raw
    map to guest = Bad User
    include = /etc/samba/dhcp.conf
    logon path = \\%L\profiles\.msprofile
    logon home = \\%L\%U\.9xprofile
    logon drive = P:
    usershare path =
    usershare allow guests = Yes
    ldap admin dn =
    usershare max shares = 100
    wins server =
    wins support = No
    mangled names = no
    dos charset = ISO8859-15
    unix charset = UTF-8
		follow symlinks = yes
		wide links = yes
		unix extensions = no
[homes]
    comment = Home Directories
    valid users = %S, %D%w%S
    read only = No
    inherit acls = Yes
    browseable = No
[profiles]
    comment = Network Profiles Service
    path = %H
    read only = No
    store dos attributes = Yes
    create mask = 0600
    directory mask = 0700
    browseable = No
[users]
    comment = All users
    path = /home
    read only = No
    inherit acls = Yes
    veto files = /aquota.user/groups/shares/
    guest ok = Yes
    # create mask = 0664
    # directory mask = 0775
    force user = andy
    browseable = yes
[groups]
    comment = All groups
    path = /home/groups
    read only = No
    inherit acls = Yes
    browseable = No
[printers]
    comment = All Printers
    path = /var/tmp
    printable = Yes
    create mask = 0600
    browseable = No
[print$]
    comment = Printer Drivers
    path = /var/lib/samba/drivers
    write list = @ntadmin root
    force group = ntadmin
    create mask = 0664
    directory mask = 0775
    browseable = No
[android_share]
    comment = android_share
    path = /home/andy/android_share/
    read only = No
    guest only = Yes
    force user = andy
    browseable = No

andy at clearmi ~ $