I have setup multiple accounts on my chessup, and I was able to sign them into different lichess and chess.com accounts. Once it is running it is very smooth, my son can just turn on the board and use his account and it just works, and then I can turn it off and use my account just as easily.
But using the app with different profiles is a bit clunky. I have to fully sign out of the app and then sign in again (one uses a Google account and the other a password). Especially if I want to get an over the board game out of the history, I need to be in the right account and it is clunky to switch. Could that be improved, like remembering all signed in accounts on the same phone?