Ubuntu-image was totally rewritten in Go for 2.0, so there are a lot of internal changes and it is clear to us now that there was not adequate test coverage for the features from the 1.11 version to accept the 2.0 implementation, but AIUI the ubuntu-image maintainers are working on it and are possibly very close to finishing the fixes so that 2.0 can be released.
Ubuntu-image was totally rewritten in Go for 2.0, so there are a lot of internal changes and it is clear to us now that there was not adequate test coverage for the features from the 1.11 version to accept the 2.0 implementation, but AIUI the ubuntu-image maintainers are working on it and are possibly very close to finishing the fixes so that 2.0 can be released.