I see the same thing as Tyler with the latest package in the Train UCA as well. In addition, I can confirm that an upgrade from the UCA Train version of ceph-mds to bionic-ussuri (proposed, verified with: 15.2.16-0ubuntu0.20.04.1~cloud0) or to focal (proposed, verified with: 15.2.16-0ubuntu0.20.04.1) works as expected, and the upgrade progresses correctly.
I see the same thing as Tyler with the latest package in the Train UCA as well. In addition, I can confirm that an upgrade from the UCA Train version of ceph-mds to bionic-ussuri (proposed, verified with: 15.2.16- 0ubuntu0. 20.04.1~ cloud0) or to focal (proposed, verified with: 15.2.16- 0ubuntu0. 20.04.1) works as expected, and the upgrade progresses correctly.