Thanks to @s3phy again for helping me understand another area where IPv6 is broken in Linux desktop networking configuration tools: connecting to a SSH server to create a SOCKS proxy using the NetworkManager SSH plugin. That thing only checks if the gateway address is a valid IPv4 address :blobpats:

I reported the issue here: github.com/danfruehauf/Network

A screenshot of the nm-connection-editor GUI for NetworkManager-SSH, where an IPv6 address has been input into the "Gateway" field. With version 1.4.1 of the plugin, it will not work.
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