Hi mad.macs,
the 3mf export is only available if you have bought the Additive Extension. Even if you were able to export the 3mf file with supports, there's no guarantee Cura would handle them as you would expect (i.e. it's not using the support bounds for Fusion bar supports, instead using their shadow to generate volume like supports; and that is after splitting the group and manually declaring supports as such).
The toolpath generation for Formlabs printers happens in their own software, whereas the other SLA printers in Fusion are MSLA printers and thus image based, not GCode.
That being said, you might get away with using a generic FFF printer, adjusting its print bed sizes and changing the post processing file (.cps) such that the generated toolpath is translated correctly to the GCode flavor your printer is using (such that extruder settings are ignored and instead translated to laser settings).
You also mentioned post processing steps in Cura, could you please elaborate?
Hope this helps, please reach out if you encounter any further roadblocks.
