Its really not that difficult to do by ear. I think you will find this faster than any software. The key of a passage or piece is the note that 'closes' or ends the piece. Most songs end on a troic chord that is a chord which has the key note as the root - unless you get that 'left hanging' feeling its going to be the root. The melody too comes to a satsfying end on the key note. Be careful often a song can change key - particularly at the bridge (the second 'different' section).
There is a good ear training software called Earmaster, it has a free trial download or used to.
If you think you have the key figured out and you find you dont, try the note a fifth down. Its quite easy to mistake the fifth for the root.

Zero


Win 11 64, Asus Rog Strix z390 mobo, 64 gig RAM, 8700k