They closed this super-critical bug despite not fixing it, claiming they're making the right decision in their implementation when they in fact misread the spec
https://github.com/systemd/systemd/issues/2514
Yeah, that's right, with resolved you cannot connect to other machines on your local network by specifying their simple names, because it blackholes those requests, and there's nothing you can do about it.
Huh? You most certainly can. I mean, somehow "ssh koyomi" works here on my network, no matter if machine I run this on uses system-resolved or unbound or something else. My DHCP server supplies options 119 and 135 and that's all that's necessary to make it work.
What you can't is to have a CNAME with a bare hostname i.e. make "foo.example.org" magically resolve to "foo.local" when you're on that particular LAN with "search local" (and $deity knows what if you're not). To be honest, I'm not even sure what's the point of this setup, unless you do split-horizon (but then why not respond with "foo.local." proper?)
Yes, I do have a "proper" domain name for my LAN and my .local is for mDNS (although I don't think I've ever used it with short names, always foo.local explicit; and I use mDNS very infrequently) - guess which is why I haven't ever seen this behavior. Thank you for clarifying.
Meanwhile, RFC4795 says that LLMNR senders should not send queries for single-label domains to DNS and that no search list should be applied to such. So querying a single-label domain does not seem likely to reach DNS on an LLMNR capable stub resolver.
My advice to one who wants to use DNS to resolve hostnames on the local network: Avoid using a domain reserved for mDNS domain and use another one.
And yes, I'm a little upset about it being broken by default and having to hunt down the issue, which did take quite a bit of time.