I have a Kubuntu 18.04 and Gimp 2.10.6 works there, I also have a PClinuxOS KDE (rpm based) and Gimp 2.10.6 installs very differently but also works.
Have you tried asking on a Debian forum? That would be the best place. I do not think there are many pure Debian users here.
An alternative is ask on https://discuss.pixls.us/ where there might be some Debian users.
When it comes to Python, I am no expert but I think some of the 'cutting edge' distro's now come with python 3 only. Check that and if required install Python 2.7
edit: just looked at the distrowatch Debian packages list and it is a 2.7.x so not python 3
Have you tried asking on a Debian forum? That would be the best place. I do not think there are many pure Debian users here.
An alternative is ask on https://discuss.pixls.us/ where there might be some Debian users.
When it comes to Python, I am no expert but I think some of the 'cutting edge' distro's now come with python 3 only. Check that and if required install Python 2.7
edit: just looked at the distrowatch Debian packages list and it is a 2.7.x so not python 3