In an Arena with three players, one disconected, Lichess get stucked and does not assign a new game

#10 In such case, like you said for 3 players, it could be feasible to arrange games manually, having two players actively playing, third one preparing for games.
1st player challenges 2nd;
1st player challenges 3rd;
2nd player challenges 3rd etc..
No need for arena. It is possible to do this way with very few players without having to make a tournament.