depends on who you ask, but my impression is they only take prints printed on official cards if you do digital. It's not the ink or the printed that matters, it's the cards.
But - I have seen people online say they've gotten printed cards approved. I also had a guy tell me he printed his manhood 20 times with an ink and FBI Cardstock and got it approved too...
FWIW…I emailed them (ATF) today after submitting Form 1. I’ll report back. Got the digital prints done at UPS store near 37 and 146. Process was quick and easy. $45. I figured it would be worth having them on hand either way.
In my interweb search for information on this matter, I did find a thread in which a guy claims he printed his male member/unit (in place of his actual fingerprints) on a print card and was approved.