cybersmog, With the help of the new Site Sets in #TYPO3 v13.1 I finally got rid of the last TypoScript template in the database. Now everything is solely file based. Hooray 💪
Next step: understand settings definitions and make usage of the Site Set PHP API.
https://docs.typo3.org/m/typo3/reference-coreapi/main/en-us/ApiOverview/SiteHandling/SiteSets.html