[massive snippage]

Thanks for the advice. Curiosity: I managed by magic, to get IPv6 working
on 'Big Metal'. Now IPv6 addressing works on the other two Windows
machines on my network. Event Viewer shows far fewer (or zero) events. But
no events related to RDP, which I use exclusively. So, IPv6 addressing is
essential for smooth RDP.

-maybe.

I should explain this so I get more advise.

For many moons, a piece of hardware gave me heartbreak. The heartbreak was
so bad I was forced to do a clean install. I lost the Gigabyte drivers. In
order to connect with to the Internet I used a wireless dongle. Then I was
able to re-install the Gigabyte Ethernet drivers. Instantly, IPv6 worked
through Hercules, HE.net. Once IPv6 works on one machine it works on all
machines on the network, that have been set up.