Help & troubleshooting for channels on your Roku device, including adding/removing channels, logging in to, authenticating, or activating a channel, channel-specific playback issues, assistance contacting channel publishers to report issues, and adjusting channel-specific settings.
Try enabling a PIN number from your online Dashboard Account. https://my.roku.com/account and navigate to PIN Preferences. (This should then preclude the Channel from automatically installing without having to input code). Can't explain why self launching on Roku startup unless remote issue (shortcut button), wallpaper/screensaver with Prime programming embedded, or possible software bug as potential reasons.
Also have to verify no one else in house is adding Prime back after you uninstall (all linked Roku devices on same account will mirror installed Channels across the devices - ie installing or uninstalling Channel on one linked device will install or uninstall this Channel on all linked devices).
Roku Community Streaming Expert Just another Roku user... I am not a Roku employee. Insignia RokuTV, Ultra 4660x, Premiere+ 3921, Express 4k+ 3941