I want the remote Linux Mint Cinnamon 20 machine to AutoStart TeamViewer on boot
Is the daemon started/enabled?
Try `sudo teamviewer daemon enable` then try again, maybe while installing the script didn't succeed enabling the service it need for remote connections.
What desktop environment are you using? Cinnamon, Matte or Gnome? Is it a wayland or Xorg session? If you are using wayland remoting into your machine is not supported, consider using Xorg if this is critical functionality for you.
In TeamViewer go to Extras > Options and check the box next to "Start TeamViewer with system"/