When coming back to work after the 23.04. / 24.04.22 my MS Teams WebApp looked somehow strange. It was even more strange, as i did not do a pacman -Syu (where i would expect something to break sometimes). So it seemed clear, Microsoft changed something with Teams and the content they distribute. As i faced a similar issue back in the days when using Todoist, i knew it had something to do with the fonts.
I dunno which fonts were distributed before that weekend, but now the current font used by MS Teams is Segoe UI, which in turn is part of Windows 10 and 11. A quick check using fc-list | rg -i "Segoe" made me realize my system is lacking that font. As i did not found a reliable source where i could download that font, i used yay to search for Segoe UI (or alternatives) in the AUR.
The AUR always delivers. Installing aur/ttf-selawik made everything fancy again. :)