FR2 is the brownish material that many cheap circuit boards are made of. It's a mixture of phenolic resin and paper. Apparently it's quite useful to make gears out of:
Phenolic Gears exhibits superior shear force, help reduce machinery noise, absorbs destructive vibration unlike metal gears, phenolic is non-conductive, protects the mating metal gear train, and are known to outlast metal gears under severe continuous service. (source: https://www.knowbirs.com/phenolic-gears )
Has anyone seen these used anywhere? I've read a hint regarding pool equipment, but I have never seen them there. I assume the fibres allow them to last longer than plastic/resin only gears.
There are some youtube videos of people machining them (sadly my browser does not support smell). Looks like you treat it like any other solid material: hobb or mill the teeth. This is much more expensive than 3d printing.
You might be surprised by your 3d printed gears. If you keep the detail size large they work really well, but backlash is definitely an issue.