Hi Ludwig,
Are you German or Austria webmaster? If yes, please read >> https://www.joomshaper.com/documentation/sp-page-builder/sp-page-builder-4/google-fonts-and-dsgvo-gdpr
similar guide we have also in SPPB 3.x documenation, where also at the end is link to video guide.
Here you can find useful tip "How to use custom fonts" >> https://www.joomshaper.com/documentation/helix-framework/helixultimate/faq-how-to-do
all basic info with video is there.
To use custom font you have to use custom CSS this is the only way now!!! It means that you have to define custom font for chosen HTML tags (body, li, a, p, h1...h6) of course first disable Google Fonts etc. in Template Options > Typography