Ask away, there are plenty of people her who have personal 3D printers. You are pretty brave printing a derailleur hanger with the Ender 3. I don't even offer anything like that printed on the professional HP MultiJetFusion printers, never will either. But it would prevent any real damage to a derailleur in the event of a crash as the plastic would likely give way long before an aluminum hanger would. I would be skeptical of the printed threads for the derailleur mounting bolt, as printed threads are just not very strong.

I do have a question about its use and practicality. Did you notice any difference in shifting performance using a printed derailleur hanger over the original metal one?