I also had screen tearing issues immediately on startup into the mint installer. Had to run the installer in safe mode to get mint going. Once mint was fully installed and rebooted to my desktop for the first time, had the same screen issues as I did with the installer not in safe mode. So mint only worked during install and only in safe mode.
Maybe our issues are similar (I’m Nvidia 1080 card), but I was never able to fix mine.