This sounds like a locale problem. Or alacritty is loading a different font (for example if you have mononiki font from 2 sources with the same name - one with glyphs and one without).
You can also check yay -Qe for difference in installed packages. There may be some critical font package missing.
Other than that you can compare your config with tools like kdiff3 or meld to spot even the tiniest difference. Depending on how “same” are your 2 system it may be trivial task (or not). If you have the same packages with the same configs then there should be no difference between Arch and EndeavourOS.
This looks like a problem with UTF-8 encoding. One of the systems have probably ISO-8859-1.
But that difference should be visible in /etc/locale.conf and/or /etc/locale.gen. Unless you have some locale change in user’s home configs directories (e.g. $HOME/.locale).