With an obvious error comes an obvious fix. One of my packages was held back during apt upgrade
user@host:~$ sudo apt upgrade
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Calculating upgrade... Done
The following packages have been kept back:
libc++1
0 upgraded, 0 newly installed, 0 to remove and 1 not upgraded.
And apt dist-upgrade was not upgrading either.
user@host:~$ sudo apt dist-upgrade
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Calculating upgrade... Done
The following packages have been kept back:
libc++1
0 upgraded, 0 newly installed, 0 to remove and 1 not upgraded.
It had to be upgraded by installing it.
user@host:~$ sudo apt install libc++1
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following additional packages will be installed:
libc++1-12 libc++abi1-12
Suggested packages:
clang
The following packages will be REMOVED:
libc++1-11 libc++abi1-11
The following NEW packages will be installed:
libc++1-12 libc++abi1-12
The following packages will be upgraded:
libc++1
1 upgraded, 2 newly installed, 2 to remove and 0 not upgraded.
Need to get 264 kB of archives.
After this operation, 25.6 kB of additional disk space will be used.
Do you want to continue? [Y/n] y
After that do-release-upgrade worked.