So far, all answers here are from mere theoreticists ... e. g. about the necessity of a heated print bed due to greater shrinkage of ABS etc. pp. The OP's question is unanswered yet.
So nobody printed ABS with the Flux 3D printer yet, right?
I tried - and did not succeed. The clear ABS 1,75 mm filament I got simply does not pass the nozzle at all. Maybe because I didn' manage to adjust the nozzle temperature to 240°C - the Flux software seems limited to 220°C when changing filament.
The filament originally distributed with the printer was PLA, obviously. After cleaning the nozzle PLA ran through again fine.
Unfortunately the nozzle is a bit difficult to remove. There is not enough space for a wrench as long as the plastic cover is in place, and when removed there is neither space enough for holding the heater when applying torque to the nozzle 8-(.
A heated print bed is no rocket science - but how to increase nozzle temperature so that ABS melts an passes through?