Thanks for letting us know what you're seeing. Please send me a PM with your Roku account email address, the serial number of your TV from Settings>System>About and a recap of the specific streaming channels, HDMI input devices/sources and content examples that you are experiencing an issue with. I'll follow up with you directly to help investigate further.
My TCL 6 Series updated to the 9.x OS the other day. On 8.x everything worked almost flawlessly. Now after installing 9.x, the ATV 4K does not even give Dolby Vision as an option. And it won't even auto switch to HDR10. While my FireTV 4K stick and Philips UHD BD player still have no problems sending DV. And DV from my XB1X does work with the TCL now. Although 9.x must have changed some settings with the TV. Because now the tone mapping is terrible and DV is too dark. And it is very slow to switch when the colorspace changes. Is there a way to roll back to 8.x? Since that version was almost perfect. And worked great with all my devices. While 9.x has definitely taken a few steps backwards. What was once a great picture is now mediocre.
I tried my other ATV 4k in the TCL setup and had the same results. I've also rebooted the devices multiple times with no change. It's really frustrating to go from having an almost flawless setup to one that now has a bunch of issues. All because of a software update.