Okay so everything so far aside; I did a distro-update on my debian laptop and am getting the following error when trying to run the RawTherapee appimage. needless to say it doesn’t even start up 
Gimp one works however.
libpangoft2-1.0.so.0: undefined symbol: FcWeightFromOpenType
stefan@stefanTHINKPAD:~/APPS/RAWTHERAPEE-4.5$ uname -a
Linux stefanTHINKPAD 4.9.0-6-amd64 #1 SMP Debian 4.9.82-1+deb9u3 (2018-03-02) x86_64 GNU/Linux
Update:
Funny enough, the appimage that is on the rawtherapee downloads page (the one that needed changes and wouldn’t run on my desktop) now works on the laptop.