In his statement on the Sinquefield Cup Scandal, Magnus Carlsen said "for my part going forward, I don't want to play against people that have cheated repeatedly in the past, because I don't know what they are capable of doing in the future. [...] So far I have only been able to speak with my actions, and those actions have stated clearly that I am not willing to play chess with Niemann."

Non-FIDE-rated matches like most online matches or friendly matches don't count. Blitz and Rapid do, if they are rated.

EDIT: I will count games aborted midway through and games retroactively made to not count towards FIDE rankings, since they fit the spirit of the question of whether Carlsen will play Niemann again. In the same vein, I won't count games which have officially started but in which Carlsen never makes a single move (eg not showing up on tournament day), or resigns after one move, like in the Julius Baer Generation cup.

(Lmk if this doesn't seem reasonable)