There is already a new interface-type setting coming in the next release, where you can select either wired or wireless. Would that address your use-case?

so does that pick up the first wired interface? What happens if there multiple links? I normally just have one wired interface but its name is different based on computer or the ethernet dongle I use.

It will choose the first one it finds. If you have multiple wired interfaces, your glob en* will probably match all of them as well.

True. As long as this new interface-type does not require explicit interface name I think I'll be fine but globs are probably more flexible? They also match how systemd-network deals with the same issue. An example of /etc/systemd/network/20-wired.network:

[Match]
Name=en*

[Network]
DHCP=ipv4

Yeah, globs or regexes are definitely more flexible. If anyone wants to implement this, PRs are welcome. Make sure to also comment here, so that we know you are working on it.

Either globs or regex are fine. Using glob (man 3 glob) is more user-friendly but is tied to the filesystem (cannot write tests for it) and I'm not sure how safe it is to pass user-supplied data to it (can it crash the process?). Regex is more flexible and is directly supplied in the standard library.

Great, I'll have a go at this weekend

Perfect 👍