Thanks for all the replies.
For ~48hrs there were no updates available through pacman. But updates were available today via pacman -Su. The first update was pretty large and included both the mainline and lts kernels, as well as, the cachy-rate-mirrors package. I rebooted but yay still failed with the same error. Attempting to install paru resulted in an error very similar to the errors yay was throwing. Then a few minutes ago I ran pacman again and it updated llvm and a few associated packages. Lo and behold yay started working, I was able to install paru and update via it.
I have no idea what went wrong and how it was fixed.