Let's get started, then. We won't just stick to theory. I'll use Firefox as an example and put it into practice, without using TOR. Let's see if it works, shall we?
Edit.
I couldn't do it. If you don't connect to the Tor network, forget it. Even following these instructions from Proton didn't help. The funny thing is that the AV and the extension block all .onion URLs as malicious.

It's always the same thing, I changed the DNS, disabled it, and tried everything, but it always ends up with "Unable to access this site."