Like every intelligent person, I hate systemd. But Linux seems determined to undo all good things, and Debian has adopted it.
In my Ubuntu 22.04 install, I’d disabled it and gone back to normal resolv.conf resolution. That didn’t work for 24.04. So I had to figure out the stupid resolution the systemd way.
To fix DNS on Ubuntu 24.04 — which, I will note, works perfectly for every other system that gets provisioned from my DHCP server — I had to go into /etc/systemd/resolved.conf and uncomment a bunch of stupid crap.
...
[Resolve]
DNS=(my DNS server IP address)
...
Domains=(my local domain)
DNSSEC=yes
...
DNSStubListener=no
...