I tried the latest 450.57 driver on Ubuntu 20.04. I have a Razer Blade 15 with an RTX2060, using a triple-display setup (the integrated 1920x1080 one, one AOC 1440p 25" on the HDMI port, and one AOC 1440p 25" on HDMI through an Aukey USB-C adapter). This works fine on 440.82 and kernel 5.6.14, but using 450.57, on both kernels 5.6.14 and 5.8rc, the USB-C display at 2560x1440 59.95Hz (the native resolution/frequency) shows an “Input Not Supported” error message. If I turn it down to 1920x1080@60Hz, it works. Reverting to 440.82, it works fine again at 2560x1440.
I tried another display (Iiyama 24" 1080p), which showed the same behavior with an “Out of range” message displayed, at email@example.comHz. Tuning down to firstname.lastname@example.orgHz made it work however, so it looks like there are some issues with the display refresh rate not being properly handled through USB-C at the native display resolution, using driver 450.57. Again, works fine with 440.82.