Hello to all of you. I also received this notification from google. you need to update the app before august 31 to the new standards, i.e. the app must be targeting Android 13 (API level 33) or later. This is only possible if MIT app inventor releases the update by that date. At the moment, from comments prior to mine, it appears that the update should be released around August 26. Anyway, I recommend to all of you, what I did: it is possible to ask google for a time extension on the update to API 33. This deferment puts the deadline at November 1. I advise all of you developers to make this request. It is usually granted. So we have more time to update our apps.
I am still waiting for communication from MIT app inventor developers.