Pretty impressed how well that one turned out. Used SUNLU TPU in yellow with 200/50 degrees Celsius at 20mm/s speed on my Voxelab Aquila (upgraded PEI bed and DirectDrive, also used Filament drybox).
This filament to be exact:
Angebot: SUNLU TPU Filament, 1KG Flexibles 95A TPU 3D Drucker Filament 1.75mm Maßgenauigkeit +/- 0.03 mm, Hohe Liquidität und Elastizität, 1KG（2.2Lbs) Spule, TPU Filament für FDM 3D Drucker,TPU Gelb https://amzn.eu/d/7H5TLjr
I think that heavily depends on the used printer, parts and filament.
But one tricky thing that comes to mind instantly was e-Steps. I got a metal dual gear Extruder and didn’t realize that the gear was smaller than the original. Because of that I had to change the e-steps in the printers firmware-settings so it knows how much it needs to turn in order to get one mm of filament through. As I didn’t know that I had some crazy underxtrusion and warping problems. Took quite a while to figure out (not only a problem with TPU).
But generally if your partner wants to get into TPU printing, I would get at least a direct drive upgrade. TPU is a flexible material and it’s better to press it in the Hotend as directly as possible. Also print very slow to get better results.