Fonts issues

Fonts and Custom domain urls caveats

Google documents caveats about using some fonts on custom domain urls - https://support.google.com/sites/answer/9068867#zippy=%2Ccaveats 

"Web Safe Fonts

Google Fonts are served as web fonts as part of every Google Sites page. 

Google Sites also allows site editors to select additional fonts, also available in Google Docs and Slides, even if not listed in Google Fonts. These fonts are licensed to Google for use on Google’s domains, but do not work with custom URLs. 

However, a small selection of "web safe" fonts will work for site viewers using Microsoft and Apple operating systems. Site viewers using ChromeOS, Android, and other operating systems that do not have these "web safe" fonts installed will see alternative fallback fonts on sites with custom URLs."

Additional Known issues

On any single Google Sites page,

1 - If there is any reference to a font which is not available to non-google domains it is possible for that one non-available font to affect the display of other fonts in that page. This issue will happen for any font which is not available to non-google domains.

2 - The presence of google-only fonts also prevents the loading of other fonts for that particular page