error: failed to prepare transaction (could not satisfy dependencies)
:: installing expat (2.7.2-1) breaks dependency 'expat=2.7.1' required by lib32-expat
I've temporarily fixed the issue with:
pacman -Syu --ignore expat
I managed to get it installed properly by ignoring expat first. After that initial update, it found an update for lib32-expat and I was able to update them together.
Yes, it would appear that the lib32 version was built and uploaded a few hours ago, thank you! (https://packages.artixlinux.org/packages/lib32/x86_64/lib32-expat/)
That's normal and happens from time to time with lib32. Just wait and try it later.