The GIMP project reports that
GNOME contributor "balooii" has worked to package GIMP
0.54.1—released in 1996—as a Flatpak that will build and
run on modern 64-bit Linux systems. This is a Motif-based
version, and the same version that was used
by Larry Ewing to create Tux.

While not likely to be useful for serious graphics work today, it
should...