Lichess does not recognize 2x Knight vs King on naked board as a draw

I had a totally drawn theoretical position with the opponent having 2 Knights vs my King on a naked board. Lichess does not seem to recognize this and gave a win (on time) to my opponent. I had sacrificed a rook to get there...had I known...can you please fix this.

6.9 Except where one of Articles 5.1.1, 5.1.2, 5.2.1, 5.2.2, 5.2.3 applies, if a player does not complete the prescribed number of moves in the allotted time, the game is lost by that player. However, the game is drawn if the position is such that the opponent cannot checkmate the player’s king by any possible series of legal moves.

With two knights against a bare king there exists a series of legal moves that leads to checkmate, hence you duly lost on time.
If you dislike that, then play with increment so you can demonstrate your defense.

OK, thanks - did not know that by "cooperation" one can bring this to a legal mate...

Exactly. When defending against two knights on the naked board the only thing you need to do is to keep your king as much closer to the center of the board as possible. Just do not bring your king towards the corner and you will never get mated. But bringing your knight to the corner helps your opponent in most endgames, including this one.

"bringing your knight (king) to the corner helps your opponent in most endgames"

• There are exceptions, like K+c vs. K+Q, or K+R+P vs. K+R.