Due to changes in systemd for bug 1849156 this issue now happens.
On an upgrade for people that had chrony installed on a do-release upgrade it now will:
Calculating the changes
MarkInstall systemd-timesyncd:amd64 < none -> 245.4-4ubuntu1 @un uN Ib > FU=1
Removing: chrony
MarkDelete chrony:amd64 < 3.2-4ubuntu4.2 -> 3.5-6ubuntu3 @ii umU Ib > FU=0
That isn't what users want, those who had chrony installed would want to get chrony upgraded and systemd-timesyncd (which now is a separate pacakge) not installed.
I'd ask you to revise the dependencies that got changes in systemd 245.4-2ubuntu1 so that on an upgrade from e.g. Bionic chrony stays installed as that was an opt-in chances are quite high people would want to keep it that way.
Due to changes in systemd for bug 1849156 this issue now happens.
On an upgrade for people that had chrony installed on a do-release upgrade it now will: timesyncd: amd64 < none -> 245.4-4ubuntu1 @un uN Ib > FU=1
Calculating the changes
MarkInstall systemd-
Removing: chrony
MarkDelete chrony:amd64 < 3.2-4ubuntu4.2 -> 3.5-6ubuntu3 @ii umU Ib > FU=0
That isn't what users want, those who had chrony installed would want to get chrony upgraded and systemd-timesyncd (which now is a separate pacakge) not installed.
I'd ask you to revise the dependencies that got changes in systemd 245.4-2ubuntu1 so that on an upgrade from e.g. Bionic chrony stays installed as that was an opt-in chances are quite high people would want to keep it that way.