Specifically, arch wasn't running any zero-conf services out of the box. CUPS would auto-detect the printer just fine, but then try to connect to it via an mDNS hostname, and the connection would fail. Once I figured that out and got mDNS working, it's been reliable.

A lot of wifi problems are due to bad/flaky access point hardware. Notably, a lot of the internet recommended "good" consumer wifi gear actually sucks from a reliability point of view. It took me months to get my home setup reliable enough to take it for granted.