To follow up on this, I filed my TY2019 lawful money tax return on paper and left the question at the top of Schedule 1 blank:
At any time during 2019, did you receive, sell, send, exchange, or otherwise acquire any financial interest in any virtual currency?

Didn't answer it at all and yet I did receive my tax refund as requested. So it appears answering that question was voluntary after all, and TurboTax just decided to make the answer required when it really isn't.