I use the Belkin USB-C to ethernet adapter for my MacBook Pro 16" with macOS Catalina 10.15.6.
When I plug it in, especially after the Mac has rebooted, macOS struggles to perform certain operations (opening apps - bounces forever, showing the dock, etc) - it's just like a freeze but I can still interact with the mouse.
When I plug out the adapter, any outstanding operations are performed instantly.
I should mention, that after a while when the adapter is "warm", everything works as expected. No freezes and I can open Apps as usual.
In every state when the adapter is plugged in, I do have a working internet connection, even when the Mac freezes.
Have any of you experienced the same strange behavior or are there any pitfalls with the hardware and software configuration I could have overlooked?