Hello Panagiotis,
Among the prerequisites there is the "python-is-python3" package which symlinks /usr/bin/python to python3.
The workstation has a slightly older Ubuntu version installed (18.04 LTS) and does not find this particular package for installation. I do not have rights to perform a system upgrade / or install a newer Ubuntu version.
On Ubuntu chances are that python already defautls to Python3 anyway, so that package may not be needed.
Is it safe to omit this package from the prerequisites?
In any case, Python3 is only required by kuibit (simfactory works with both Python2 and Python3), so if you do not plan to use kuibit then you do not need python-is-python3
Are there elements in ET that are possible to "break" if this is left out? Is there a workaround, for example should I do the symlink to python3 manually?
The only one that comes to mind would be kuibit. A workaround would be (if any of the kuibit helper scripts use "#!/usr/bin/python" instead of "#!/usr/bin/python3") to call them via Python, ie
python3 plot-2d-data.py mysim
instead of
plot-2d-data.py mysim
Yours, Roland