Lichess will flag your account as a cheater w/o notifying you so that your opponents see the flag and avoid games. I know this because a friend of mine who is an average player got flagged that way after a stretch of games he won handily, including one against me where I checked computer analysis and noticed he made zero incorrect moves. A red flag popped up next to his screenname, I asked if he was aware of it and he said he couldn’t see it and got no notification of it.

I love the shadow flag method for cheaters because opponents can avoid games with them and the cheater may never figure out what the problem is.