I have an Apple Watch Series 7 with original charger and plugged into a 3rd party brick and running 8.3 Beta 1 no issues. The issue at hand for some users is reasons why I use Apple only chargers. When I had an iPhone 7 and 8 and used third party chargers it would brick my phone, could do anything also would send it in a loop if I factory reset it. So from then on I told myself I would only use Apple products with Apple products.