2 devices,... the problem and solutions are below.

The first problem was with an error running sudo apt update with it freezing on a line similar to...
"Connecting to archive.ubuntu.com"
Solution here:
https://medium.com/@muhammadtriwibowo/fix-apt-get-update-stuck-connecting-to-security-ubuntu-com-2471aa425d83
--- relevant section from referenced site ---
That problem caused by apt-get try to connect IPv6, so to resolved that issues, we just need to disabled IPv6 via /etc/sysctl.conf

Add the following lines at the bottom of /etc/sysctl.conf:
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1

Then, after add these lines, just run sudo sysctl -p to reload the /etc/sysctl.conf settings.
--- end section from referenced site ---

The second problem was with running sudo apt update, which gave an error similar to...
"The following signatures couldn't be verified because the public key is not available: "
Solution here:
https://askubuntu.com/questions/1103320/the-following-signatures-couldnt-be-verified-because-the-public-key-is-not-avai

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