YouTube used to have an open feed for any search term, but they took it away. This seems to have search but I don't know if you need to authenticate first.

I use YouTube RSS and the most annoying thing is that it doesn't use the conventional date stamp, which is very annoying. That's a problem worth fixing.

Humm, I don't think I had this be a problem. Likely TTRSS ignores this issue and/or just parses the timestamp until numbers come out.

Or perhaps those feeds are deficient in some way. Maybe they update later than the actual site, or have ads inserted as if they are articles.

Neither of those three do that to my knowledge.

Well, given Steam is basically 90% just announcements for deals and HN is an endless spam of articles that were on the frontpage for a millisecond, but I think that would be given.