Block all websites and add few using NextDNS

Use NXEnhanced to block all TLD, then add the domains you want to use to allowlist. Note that most sites use multiple domains, some of the dependencies are shared, and NextDNS has no context about where you're loading the domain, so, for example, you allowed domain X because you want it to load images on website Y, you don't get to tell NextDNS to not load domain X when it's used by website Z.