Comment 8 for bug 1619921

Took some additional digging, but already confirmed, and definitely yubikey-luks side of the fence... it was using a non-public interface.

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=904162#15

Looks like there was some refactoring, and ostensibly this is fixed in a later iteration of yubikey-luks that is in U19.04/Disco but not U18.10/Cosmic at present

https://bugs.launchpad.net/ubuntu/+source/yubikey-luks/0.5.1+29.g5df2b95-1

U18.10/Cosmic, U18.04/Bionic, et al are on

https://bugs.launchpad.net/ubuntu/+source/yubikey-luks/0.3.3+3.ge11e4c1-1