For me also Twitter is the number 1 source. Most AI researchers are active on Twitter so by following them you get new breakthroughs and paper notifications straight from the source (i.e. the authors).
As for sources not already mentioned, I can highly recommend Yannic Kilcher’s ML News series on Youtube to stay up to date with new developments.
this is what I currently use + Google scholar/scopus automatic emails.
I personally really dislike twitter and think it’s over rated + has lots of secondary really negative side effects instead of side benefits (e.g. ppl fighting, twitter trying to sunk in your time and attention, etc).