"All the options I received (in 2017) from joining a board were exercised as a result of a change in control transaction in 2021"

I think you mean exercised and sold in 2021.

The fees for serving on the board would have been on 1099-MISC/1099-NEC. 

The sale of the stock acquired by exercising the options would probably have been reported on 1099-B, but if it was a small privately held company it may not have been.

Anyway, you surely received, and probably signed, some paperwork regarding this 2021 transaction. Give that to your accountant.