I am trying to change the Samba workgroup from its default WORKGROUP to something else.

I managed to fix it. By going to

System Preferences->Network->WiFi->Advanced...->WINS-> WINS Servers

and adding the IP address of my network router as a WINS server.

This enabled me to change the Workgroup from WORKGROUP to HOME.

I'm afraid I have mislayed the reference for this suggestion.

I now have other problems. I cannot connect, neither from Ubuntu to Mac nor Mac to Ubuntu. I am now wondering, do I need a Samba server? Am I misleading Samba by specifying my router as a server? Does Ubuntu have a built in Samba server that is already running?

Barney-15E wrote:

I don't know if Ubuntu comes with Samba installed and configured out of the box. You may have to at least configure it to run, but you may have to install Samba on it.

I have sorted this out to the extent that the Mac can now see the other machine, so Samba definitely seems to be running on Ubuntu as a default. On Ubuntu I edited the Samba configuration file to make Workgroup=HOME.

On the Mac I went to

System Preferences->Network->WiFi->Advanced...->WINS->WINS server

and added the IP address of the Ubuntu Mate. I don't know if this was necessary.

I think this problem is solved, but I have now run into a different problem. (See this question.)

Thanks for your help.

Barney-15E wrote:

I don't know if Ubuntu comes with Samba installed and configured out of the box. You may have to at least configure it to run, but you may have to install Samba on it.

Some more things I have noticed which may suggest that Samba is running as a default server out of the box?

    $ ps -ef | grep smb
    root      1286     1  0 Apr25 ?        00:00:00 /usr/sbin/smbd -D
    root      1288  1286  0 Apr25 ?        00:00:00 /usr/sbin/smbd -D
    root      1326  1286  0 Apr25 ?        00:00:01 /usr/sbin/smbd -D
    bob       6765     1  0 Apr25 ?        00:00:00 /usr/lib/gvfs/gvfsd-smb-browse --spawner :1.9 /org/gtk/gvfs/exec_spaw/8
    bob      24684  5123  0 20:22 pts/0    00:00:00 grep smb

    $ sudo nmap -sS -sU -T4 192.168.0.110
    Starting Nmap 7.01 ( https://nmap.org ) at 2021-04-25 19:44 CEST
    Nmap scan report for 192.168.0.110
    Host is up (0.000049s latency).
    Not shown: 1990 closed ports
    PORT     STATE         SERVICE
    22/tcp   open          ssh
    80/tcp   open          http
    139/tcp  open          netbios-ssn
    445/tcp  open          microsoft-ds
    68/udp   open|filtered dhcpc
    123/udp  open          ntp
    137/udp  open          netbios-ns
    138/udp  open|filtered netbios-dgm
    631/udp  open|filtered ipp
    5353/udp open|filtered zeroconf

I looked at the link you gave me, but Samba do not appear to have a discussion forum, only a non-searchable mailing list archive. Thanks anyway.