The FreeMono font is used to display Perso-Arabic glyphs, which doesn't have a very pleasant appearance. The noto-fonts package is installed, which provides nicer-looking glyphs. The Arch Wiki mentions this problem and provides two example fontconfig files that ought to fix it. If I recall correctly, I tried all permutations of both files in user-specific and system-wide fontconfig files; however, this seemingly had the effect of making Firefox's UI use Noto while website content and other applications: Kate, clipboard widget (I run KDE Plasma) etc. continue to use FreeMono.
Any help would be greatly appreciated. Thank you!