vtk6 cannot be installed on (my) Ubuntu 20

The following 1 apt packages are required but not installed yet:
┏━━━┳━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
┃ # ┃ Apt Package Name ┃ Myodule(s) ┃ Directly Dependent Modules ┃
┡━━━╇━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━━━━━━━┩
│ 1 │ vtk6             │ apt/vtk6   │ affordance-kit             │
└───┴──────────────────┴────────────┴────────────────────────────┘
Run 'sudo apt-get install --no-install-recommends -y vtk6' to install 1 package? [y/N]: y
Run 'sudo apt-get install --no-install-recommends -y vtk6' ...
────────────────────────────────────────── Command output ───────────────────────────────────────────
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 vtk6 : Depends: libvtk6.3 (= 6.3.0+dfsg1-11build1) but 6.3.0+dfsg2-5build2 is to be installed
E: Unable to correct problems, you have held broken packages.
─────────────────────────────────────────────────────────────────────────────────────────────────────
Error: Running 'sudo apt-get install --no-install-recommends -y vtk6' failed with return code 100.

Can be fixed by switching to VTK7 on Ubuntu 20. Need to check whether everything builds. However, it should, as this my setup is like that for some time now.