I would ask on https://discuss.pixls.us/ (although they are very Darktable biased these days)
FWIW: I turn colour management in Preferences off and apply on a per-image basis from the View menu. A bit tedious since you need to re-open the same menu for each setting.
Might go like this 50 second demo: https://i.imgur.com/1bW5jYr.mp4
I use gutenprint as well, monitor is not calibrated but brightness is turned down and I know the printer 'tweaks'
FWIW: I turn colour management in Preferences off and apply on a per-image basis from the View menu. A bit tedious since you need to re-open the same menu for each setting.
Might go like this 50 second demo: https://i.imgur.com/1bW5jYr.mp4
I use gutenprint as well, monitor is not calibrated but brightness is turned down and I know the printer 'tweaks'