An interesting rook endgame I've noticed recently. Carlsen - Keymer, 2023

I had watched the games of the FIDE world cup 2023 in real time via chess.com/events, having a really great time. Magnus Carlsen & Vincent Keymer played against each other on the 4th round and their chess battle seemed to me perhaps the most fascinating of the cup.

The following game reached to a point where black had really few choices to keep the position equal; maybe only one move which wasn't played. It wasn't easy for me to understand it while watching it, and I had to download it and play it through engines.

I think that first it should be understood the main white's threat. Then can you find the best move for black here?

... it's 52... Be2

 
the game

... thank you for reading!