The forum references the following font files, but they are gone.
I’d say we should remove them from the theme then.
Okay, I built a new Font theme component, which locally sources all OpenSans fonts instead of pinging nextcloud site. Should fix this issue for you.
It looks fixed to me with the default theme
I’m still seeing the failing requests with “Discourse Theme Switcher”
That is because I didn’t touch that theme. We could remove it, or you can alter the theme to use font assets component instead of font.