I suppose relying on LINGUAS files only would allow us to have different set of languages for each domain. It just be confirmed that everything would work even with the oldest gettext version that we support (with the option to bump that minimum requirement, of course)
Saw "setting ALL_LINGUAS in configure.in is obsolete" in configure output. Master, msys2-220309.
Quick look indicates that po.m4 says that when LINGUAS -file is present. We've added those for the benefit of meson based build.