I'm glad it works so well for you on Ubuntu. For some reason it
doesn't work well for me on Kubuntu. Maybe I'm missing something
obvious but it has me puzzled.

I created the ip address bookmarks in the Dolphin File Browser and
nothing would connect. Every other machine timed out - very quickly.
What I had to do to get access was go to each machine. Stop Samba in
gadmin-samba, restart Samba, which then showed winbindd (2 d's) as an
inactive server. On the CLI sudo winbindd and the password brought
Samba to life. I've just done this on 3 machines and I'm sure the last
one, our Home Theatre, connected to the large screen TV as monitor,
will be the same.

Can you see anything I'm doing wrong, short of using Kubuntu insteasd
of Ubuntu? I've got this routine down to a fine art over several years
and it always works, but it shouldn't be necessary and that's what I'm
wrestling with...