This was my first idea, I tried setting DNS to 8.8.8.8, tried 1.1.1.1, tried others, tried setting them in Network Setting, tried on router, tried sudo killall

This was my first idea, I tried setting DNS to 8.8.8.8, tried 1.1.1.1, tried others, tried setting them in Network Setting, tried on router, tried sudo killall -HUP mDNSResponder. I can ping those faulty websites during Safari downtime without issue, but somehow the browser does not even try opening the website (Timeline Recording in Safari shows no Network Requests). It looks like macOS is caching something somewhere and when that cache expires it starts to work again. Emptying Safari caches does not help and I don't know if there is any way to purge all system networking caches. Chromium based browsers certainly ignore something, it might be DNS related but I'm out of concrete ideas what exactly to change.