Steel rims banned?

Good morning, I was with the Audi partner yesterday, because I am currently looking for winter tyres. There there were very nice Audi original Alusals factory offer with Dunlop 205-55-16 for 185 euros. When I wanted to buy these, the part seller told me that I should not drive these rims, with the 225 hp coupé only rims with a press-in depth of 32 mm are allowed and there I would have “surely difficulties to find cheap!”. She could give me some for about 380 euros per piece. When I then approached steel rims, I was told that I should not drive them at all. My question now is: Does anyone know cheap aluminium rims approved for the TT? Or can I have smooth rims (e.g. the RH “MX Snowline” in the workshop or just registered with the TÜV directly? And what does that cost in some way or is this a big effort? And can I really not drive steel rims? Thank you, Best regards marcus