It’s not AUR yet, there’s just one remaining test that fails on Arch currently. Related PR fixing this is right here: cmd: pretend we're running on Ubuntu in TestExecInCoreSnapUnsetsDidRe… by bboozzoo · Pull Request #4235 · canonical/snapd · GitHub
Other than that, can you clone snapd repository and follow instructions from this post Updates to snapd package on Arch - #35 by mborzecki ?