SGI IRIS 2000
sgi iris 2500T
sgi iris 3130
https://en.wikipedia.org/wiki/Sun-1
https://en.wikipedia.org/wiki/Sun-2
https://en.wikipedia.org/wiki/Sun-3
https://en.wikipedia.org/wiki/HP_9000
https://en.wikipedia.org/wiki/HP_series_80
https://en.wikipedia.org/wiki/HP_9845C

note that some of these are 68000-based systems, and a few of those I want to look up for my own interests — especially since those would probably will just suffice with the GTK+ 3 port assuming a modern unix-like system can be run on them

IRIX {
007-2006-120.pdf
http://irix7.com/techpubs/007-2006-120.pdf

007-2006-130.pdf
http://irix7.com/techpubs/007-2006-130.pdf

007-2167-005.pdf
http://irix7.com/techpubs/007-2167-005.pdf

007-2167-006.pdf
http://irix7.com/techpubs/007-2167-006.pdf

007-2006-080.pdf
http://irix7.com/techpubs/007-2006-080.pdf

007-2006-090.pdf
http://irix7.com/techpubs/007-2006-090.pdf

007-2006-100.pdf
http://irix7.com/techpubs/007-2006-100.pdf

007-2167-001.pdf
http://irix7.com/techpubs/007-2167-001.pdf

007-2167-002.pdf
http://irix7.com/techpubs/007-2167-002.pdf

007-2167-003.pdf
http://irix7.com/techpubs/007-2167-003.pdf

007-2851-001.pdf
http://irix7.com/techpubs/007-2851-001.pdf

007-1472-020.pdf
http://irix7.com/techpubs/007-1472-020.pdf

007-1797-020.pdf
http://irix7.com/techpubs/007-1797-020.pdf

007-1797-030.pdf
http://irix7.com/techpubs/007-1797-030.pdf

007-3951-001.pdf
http://irix7.com/techpubs/007-3951-001.pdf
} GTK+ is not an option because of no dbus, but maybe we could get away with mixing Motif and some 2D library that's in IRIX itself? but which one?...