Thanks Ed, that gets us closer to the root cause.
rubygems.org - works on host, inside the container:
Connecting to rubygems.org (rubygems.org)|151.101.1.227|:443... failed: No route to host.
But
wget -O /dev/null https://google.com
Works just as it should. Mayhaps rubygems still has a problem. I guess I am going to try on Monday again.
Since google works, I think I can assume the setup is correct, meaning the problem seems to be outside of my control.
Thanks again for the troubleshooting help.