The biggest problem people have with Tinkerboard when switching to mainline kernels is the lack of supported HDMI resolutions.
This generally result in a “TinBrokeBoard” .
I found this patch in LibreElec.tv patches list (they have MANY HDMI patches actually), and thought “That might be the one that enable more resolutions”.
The patch add more PLL configuration, so that the HDMI clock can meet the requirements for various other resolutions.
Unfortunately for me, I only have normal screens, so that needs to be tested by people who have like 4/3 screens, or VGA->HDMI, DVI->HDMI dongles and what nots.