For anyone having trouble getting the synchack program to work and always getting 'unknown error!' Here is how I did it. This is for mirror link only.
Follow the above steps with that file. Note this will install mirror link in the apps screen, not running off USB like SyncAppRunner.
Unzip the archive but use WinRar, for some reason when you unzip with Windows, it changes the timestamps of the files and throws an error "bad files

"
Check the unzipped files and ensure they don't all have today's date as "date modified" there should be some files that have a date of 2018.
Then when in the root folder on windows of the folder you unzipped with "decrypt.exe" visible, type CMD in the top Windows "address bar" where it shows the folder path. It should open the CMD prompt in the selected directory.
Then type "decrypt S/N" where S/N is your 8 digit serial number from Sync 2.
The function should now work. And you will have new files created in the root folder.
Then follow the above steps starting at step 5 to install in your vehicle.
Note this method apparently disables the wallpaper.png exploit and to install any other program you need to reset Sync to factory settings.
I am going to try using the SyncAppRunner that was modified by a user here to install the newest EasyConnection server program on Sync and report back if it works better.
The other option is to follow Sensorial's steps a few posts back and purchase the Carlinkit dongle and have them create the install file for you, this will allow carplay or android auto on Sync.
The mirror link file linked above doesn't work great, screen mirror works but no touchscreen support for Android 13, if you have an old android below Android 9 that you can use as a slave to run HUR and mirror that way while connecting your actual android to the slave that would also work with no dongle.
The easyconnected APK either Chinese or English versions linked here work with touchscreen support but it's a clunky solution because the apps included are Chinese, don't support google maps, Spotify, etc.
My other idea would be to somehow unpack the easyconnected APK and recompile it to connect to easyconn server on Sync or Autokit? but somehow run something more similar to AA, maybe with Headunit Reloaded running in selfmode. Not sure if it's possible though, in that way the touchscreen would work without needing a dongle or a slave android device.