I was having issues with the wires of my Ender 6 getting caught on the wheels and unplugging the cord for my hot end heater causing thermal runaway errors so made a cover to fix it “real quick”

If your 6 is NOT enclosed any filament type would be fine. I personally am using a TPU one until I can print ASA

If your 6 IS enclosed I'd recommend either ABS or ASA. TPU would also work but isn't ideal due to the wires squishing the part a bit when pressed on it

No supports needed as long as your printer can print 50 degree overhangs

This part is a press fit with only about .5mm of room so you will either have to make sure your retraction settings are good or do a bit of sanding if not