21" wheel owners, have you broken a wheel?

What do you mean by "broken" a wheel? Bent wheel or cracked it? There's a very big difference.

I had a slight bend on a rim, noted when I got the tires balanced. I can't feel it and didn't need to have it repaired.

I bent a 21" wheel (along with a rear link assembly!) but the tire itself survived. It happened when I hit a pothole. I paid ~$1100 for a new wheel and had the slightly bent one repaired for about $150. It is now my full size spare. I keep my eyes glued to the road for potholes now.

I hit a small pot hole @ 30 mph; rim destroyed but tire survived. bought two used 21" cyclone on ebay for $275 each + shipping.
thinking about selling all 4 wheels + current continental tires and 4 brand new V12 Hankook

I think you need to clarify whether the 21" wheel was a the Tesla OEM Turbine wheel or an aftermarket wheel.

Got around 25k miles on my first set of Continentals on the 21 inch OEM turbine wheel. No issues except for curb rash. I run them at 45 psi vs the 42 recommended.

I have the Turbine 21"s with the Michelin Pilot Sports. Staggered P85+ configuration. I got the rim bands from Evannex. Over the course of the last 8 months I have managed to hit all 4 rims. Two were in one car wash event that will never happen again. Anyway, the rim guards did their job. While this is regarding curb parking errors, it is a great protection for about $100. This won't offer protection from pot holes as discussed. But the thread is about protecting 21" rims.