Hi Mark,
Also, compare the output of fc-list(1) on each machine?
It looks like this might be the culprit. I aggressively went through the working machine and removed any font that wasn't present on the non-working machine. Now, neither machine works!
Progress! How did you remove the fonts from the working machine? Delete pacman packages containing them? Have you a record of what you removed?
So now the issue is that even though both machines have been configured to use the same font all along
No, it sounds like the same search for a font was configured on both and the search resulted in a different font. Have you perused https://wiki.archlinux.org/title/Fonts ?
clearly the one that _was_ working was falling back to some other font for the glyphs the selected font didn't have.
Or it was choosing a different font to the non-working machine for the same search criteria.
I'm not sure if there's a sane way to find out what exactly was happening there. Ideally I'd like both machines to work.
Get the working one working once again and see what matches against the search criteria configured in the program. fc-match(1) can be helpful. -- Cheers, Ralph.