Thank you for your helpful replies. Perhaps I am carrying over some
unrealistic expectations on networking from my Windows and NetWare days,
which I leave behind with absolutely no regrets.

I use Kubuntu and KDE on Linux Mint.

What I am looking for is the ability to browse the network and copy/
transfer files between any two machines, in other words, full two-way peer
to peer sharing. Naturally I'm looking for this to be stable, reliable and
seamless. There are no Windows machines on my net at present, but if they
could be added it would be a bonus. So far the stability and reliability
have been unsatisfactory. As a (retired) network administrator I always
worked towards "five nines" reliability, i. e. 99.999% uptime. With NetWare
(much as I hated Novell) we achieved it.

I guess this is just a hobby now, but I'm sure it can be done with Kubuntu,
and I will keep working on it. Maybe my next step should be NFS sharing.
I'll let you know of any breakthroughs.