There is a 'nomodeset' parameter you could add to boot.cmd to avoid KMS. Still you have to convert it to boot.scr (check last lines of boot.cmd for the correct syntax) . I'm not if it has any effect on Desktop or Kodi, as they seem to work independently changing modes on the fly.
If it works, resolution setting from /boot/armbianEnv.txt should stay (line starting with extraargs...). It's set to 720p by default.
If it works, resolution setting from /boot/armbianEnv.txt should stay (line starting with extraargs...). It's set to 720p by default.