If you find the checkmate in 2, you are genius ðŸ§
1. Rxb7+ Kxb7 2. g8=Q# (I presume you mean 1. Rxb8+ KxB8 ...
but 2. ... Kc7 (so not mate)
1. g8=B, [any bishop move form the opponent] 2. Bd5#
Do you know the forum: „If you find mate in 1, you are a genius🧠“? The mate in one was actually harder in my opinion lol.
1. g8 = B , (Black bishop could move anywhere)
2. Bd5#
White rook covers all b line, the opponent's king and bishop cannot do anything.
Rb7 wherever the bishop goes
g8#
Bishop goes back to block the check, so you've got mate in 3.