Me again sorry. Following the commit #46 fixing #51 the devel update check fails every time on my system. Pacman and AUR work as expected.
Edit: I'm thinking my memory is just bad and the issue started a few days after the update... maybe
It seems I missed an obvious point until directly after posting this, instead I'm suspecting it is to do with one of the AUR package mirrors in Australia currently being down and the check not being able to handle this. Pacman and regular AUR update checking in the applet works normally, and actually updating with yay --devel completes successfully.
error: failed retrieving file 'multilib.db' from sydney.mirror.pkgbuild.com : Could not resolve host: sydney.mirror.pkgbuild.com
warning: fatal error from sydney.mirror.pkgbuild.com, skipping for the remainder of this transaction
error: failed retrieving file 'core.db' from sydney.mirror.pkgbuild.com : Failed to connect to sydney.mirror.pkgbuild.com port 443 after 1 ms: Could not connect to server
error: failed retrieving file 'extra.db' from sydney.mirror.pkgbuild.com : Failed to connect to sydney.mirror.pkgbuild.com port 443 after 1 ms: Could not connect to server

Me again sorry. Following the commit #46 fixing #51 the devel update check fails every time on my system. Pacman and AUR work as expected.Edit: I'm thinking my memory is just bad and the issue started a few days after the update... maybe
It seems I missed an obvious point until directly after posting this, instead I'm suspecting it is to do with one of the AUR package mirrors in Australia currently being down and the check not being able to handle this. Pacman and regular AUR update checking in the applet works normally, and actually updating with yay --devel completes successfully.