key resellers have office 2021 pro plus (the non subscription one) for $30.00ish (earlier versions are even cheaper) and that is what I recommend if you absolutely have to get office.
Considering the grey market is filled with dodgy keys, it'd be better to just pirate, especially when there are easy and safe ways to do it like with MAS
Good resellers do, but I think my point still stands - why risk any of that when Microsoft doesn't get your money either way?
MAS/Massgrave works effectively, is open source, is well-documented, and literally free.