I get the occasional hung Firefox browser (browser UI works but none of the tabs render any content, or render a single tab that doesn't work). I'm not sure what's causing it, but based on the behaviour I observed, I don't think it's an addon related bug.

I wish I could reproduce it to file a bug report. These stability bugs are the reason I'm hesitant to recommend Firefox to non-technophiles, especially since the web is unusable without at least an ad blocker. While I still use Firefox, Brave seems to be doing a much better job at blocking ads without slowing down.