I once applied to an internship for a company doing job offers aggregation. During the interview they explained to me that the core of what they did was parsing (partial) html with regex. When I asked why they wouldn’t develop a custom parser, they replied to me that they were working on it, but that the internship wouldn’t focus on that. I was not disappointed when it didn’t get the job.

I don’t know a way to do it for a given system, at home you could plug a small computer to your router, like a raspberry or equivalent, set that as a dns, and run filtering on it.