Edit: copying the font to /usr/local/share/fonts/ fixed it. (I downloaded Debian Xfce a while ago because of how much I dislike Snap, so I’ll soon replace Xubuntu with it.)
I recently installed the font “Atkinson Hyperlegible” on Xubuntu 22.04.3 (via right click, Fonts 41.0), and I use it as the Xfce UI font and the default in Mousepad and LibreOffice without any problems.
However in Firefox 120.0.1 (64-bit), Snap for Ubuntu, canonical-002 - 1.0; it’s not listed at Edit, Settings, Fonts; or Fonts, Advanced…
When I view an HTML page where the CSS’ body has font-family:"Atkinson Hyperlegible",sans-serif; it also doesn’t use the Atkinson font. That page also doesn’t use Atkinson in the (Epiphany GNOME) Web 45.1 browser.
Any ideas on how to get Firefox and Epiphany to see it?
I don’t know anything about how Firefox is packaged for snap, but snap’s “sandboxing” might interfere with getting all fonts.
You might want to try using Firefox without snap (which has some other benefits, especially around startup time) or adding ~/.local/share/fonts (which is where fonts are supposed to be installed for users) to some sort of allowlist.