I want to build Gimp 2.4 (2007) for my own private repo.
Is it possible; without extreme difficulty to build local flatpaks of legacy programs for myself? I know most people have zero interest in legacy versions of Gimp from 2007. I can start by fetching all the .deb files and or source files from Debian or Canonical’s archive. I just need to know if this would be possible? Thanks, please do not go on about security risk, as this is just a tinkering thing.
What I would do is start from the gimp 2.10 manifest.
Totally possible. I say that from my experience of flatpaking an old QT3 app (from 2010, this one). Just build from the Freedesktop runtime, adding GTK2 as module on top and then your GIMP module.
You will probably encounter some build errors due to using a newer gcc (as newer means more strict with old nonconforming code) but you can easily fix those by searching those errors on the internet and patching the code about it.
No need to involve debian packages at all, just grab the source tarballs from any of the gimp ftp mirrors, for example https://www.nic.funet.fi/pub/mirrors/ftp.gimp.org/v2.4/
List of mirrors are in https://www.gimp.org/downloads/
Same way old gtk release tarballs can be found in https://download.gnome.org/sources/gtk+/
The current GIMP stable use gtk2 still.