Hi rcworcs, ok so this is interesting. If your car is a late car as yours is, it should already have the correct software upgrade to allow Tesla charging. This is borne out by the dealers saying there isn't an update to allow Tesla charging showing on the system. If your car didn't have the update/upgrade, it would show up.
So the question is, why won't your car charge on a Tesla charger. This can be because...
1. You have a glitch with your software (unlikely);
2. Your Tesla app is configured incorrectly (more likely).
Point 2 has sometimes often proven to be the case. Make sure you have selected 'Any car' as the vehicle you are using in the app. It will only work using that selection. Make sure everything else you've entered into the app is 100% correct.
To find the software 'R' number you must look in the settings for the infotainment system. You are looking for the entertainment system version number, the 'R' number. The R number is on the end of a very long number in the entertainment SYSTEM settings section. Yours will most likely be R25. I'm pretty sure 'R25' can 'see' most updates for your car including the Tesla upgrade if you need one. As mentioned, if it doesn't show a Tesla upgrade at the dealers when hooked up to the MG computer, you've already got It! R25 will not be able to see certain other updates for the cars computer modules. Only R27 (the latest) can currently see all of those. Your car will no doubt be upgraded when it goes into the dealer for it's first service. But you must make sure to ask for them to be sure it gets them.
To add, my car was registered brand new in January this year. Mine had R25 & already had the Tesla upgrade. Mine was upgrade to R27 due to a minor glitch in my software. However, every 2024 car has the Tesla upgrade & many 2023 cars too. Dunno if any of this helps.