From what I have been able to understand from reading about this keyboard on this board, the capacitors in the M2 should have a tendency to degrade when the board has not been used for a long time.
Therefore, a "mint in box" M2 is kind of a gamble: some work, some do not.
According to the seller, this keyboard was used less than a year ago, so it should have a higher probability of working all right.
Unlike the Model M, this keyboard is flat. It is also much smaller than a Model M, and less sturdy.
I am not a stranger to modifying things, and I have a few things in mind ...