<p>I recently got a Dremel 3D20, and I understand it only takes PLA filament according to the Dremel site.  However, I was wondering if anyone has successfully used TPU filament or knows it will work fine.  I’m more than happy to use other software to change the temperature, I just don’t want to gunk up or otherwise ruin my printer.</p>

TPU wants in general two things of your printer:
A Printing Temperature of (over many makers) 195-230 °C
A Direct Drive (extruder on the printhead)
Bowden extruders are not ideal for printing flexible filaments such as NinjaFlex due to the excessive
  distance between the stepper motor and the extruder head. However, some users have generated
  successful prints using reduced speeds.
ninjaflex handout
Check the temperature you can reach, and you are lucky, as some of the smaller Dremels use Bowden but the 3d20 is apparently direct drive.
If you want to try to run a Bowden with flexible filaments, dial down speed down really low (20-30 mm/s at most) and pray.