The lists are maintained same as extensions.

One thing doesn't rule out the other. Just because a browser has a built-in adblocker doesn't mean you can't replace it with another one if it's not working well. Every browser should have at least a basic adblocker enabled by default. Anything else is a major security risk. In the context of web browsers ads are the main entry point for malware. Either through exploits delivered via ad banners or by tricking users into downloading something. Many search engines such as Google display fake search results that lead to infected versions of otherwise secure software. Additionally some sites offering downloads have ads disguised as download buttons that lead to something else. A browser manufacturer should try to protect its users from such things.

I've been using ETP plus adblock-rs in Waterfox for 2 weeks. I don't see much a difference compared to ETP + ublock origin apart from some cosmetic filtering. The fact that it's not an extension supposedly allows to block at more layers so it's theoretically better than an extension (https://github.com/BrowserWorks/waterfox/issues/4182)

Note that there are (were?) also some small bugs in the waterfox integration (such as the configuration options sometimes disappearing).

You might want to not use chromium?

why use brave, really, when you have firefox? I get it if you're on iOS

  -iCloud Private Relay (native VPN-like thing)  
  -uBlock Origin Lite
  -AdGuard DNS

Genuine question, does brave have ff's container extension? currently that's one of the thing that keeps holding me on ff. another big one is i test website on firefox so to not get carried away with features only available in chromium

Why support Chrome at all?