Web Compatibility Support • Re: Suggestion for a fallback browser

My question is for a suggestion about what to do for sites which do not work with Pale Moon, with the idea of using one alternate browser., with the minimum "damage" i.e. difference from the "safe" behaviour of Pale Moon.

Cromite (https://github.com/uazo/cromite) has everything you're asking for, with a built-in content blocker. The latest version is 145, which is 2 major versions behind. Although it looks like on their GitHub they're working on it.