The issue is related to fontconfig's bug (See https://forum.snapcraft.io/t/snapped-app-not-loading-fonts-on-fedora-and-arch/12484/18).

Try the workaround here: https://forum.snapcraft.io/t/snapped-app-not-loading-fonts-on-fedora-and-arch/12484/60

Solution 1.
sudo rm /var/cache/fontconfig/*
rm ~/.cache/fontconfig/*
fc-cache -r
Solution 2.
sudo pacman -S yay
yay -S debtap
sudo debtap -u
debtap stacks-app_[ver]_amd64.deb
sudo pacman -U ./stacks-app-[ver].pkg.tar.zst