80% of panels are made in China, if they were all so terrible I doubt they would dominate the market so much

For a residential setting, installation quality probably dominates, and I doubt country of origin is statistically significant. Otherwise look at warranties which specify a performance curve over lifetime (generally 25y, also some are independently guaranteed by an insurance company that might actually survive that long). There are public performance datasets from NREL, TUV, but be careful about choosing representative examples (e.g. utility scale reliability is different from rooftop)

I meant it as a general thing. These days all manufacturers, from all countries, offer 20+ year warranties. Not just Chinese ones.

However you inspired me to do some research, and I found this: https://www.cnet.com/home/energy-and-utilities/best-solar-pa....

The article lists top PV manufacturers and their efficiency ratings, production warranty, and other statistics. There are several Chinese companies on the list with 25+ year warranties. The article's top-rated manufacturer in the category of "Longest production warranty" is ZNShine Solar, a Chinese company that offers a 30 year warranty.