Where other surfaces have the problem when the screen is heating up, I have this problem when the screen is cold.
When starting up, everything flickers, doubles etc. When warmed up after 5 minutes the surface becomes usable .
Even on hot days I have no flickering on startup. This is also a thermal problem of the screen, but sligfhtly different from others....
Maybe you have the same? When rebooting in safe mode, the screen was warmed up?
You can try starting up with a Ubuntu USB stick, so this way you can eliminate all microsoft / windows drivers that might cause this flickering.
If you still have the flickering in the ubunto desktop, you know enough. PS nothing will be installed... When you plug out the ubuntu usb stick, the regular windows will start. I hope this helps
https://ubuntu.com/tutorials/create-a-usb-stick-on-windows#3-usb-selection