Please see the second post.
days ,month .my mood off 
can u tell me why other app builder has sdk 30?like niotron
How is niotron providing SDK 30? When app inventor can't even complete it?
Please ask on that community, they will have the answer
i agree with you all right
No i was asking that because it's confusing because those builder do use app inventor's source code. Or I'm i wrong?
Do they? Seems unlikely given AI2 is not yet targeting API30, other than on the test server... 
You need to ask on Niotron Community if you need to understand how they have done it...
Well let's see if they can answer this question.
Yes, other distros are based on AI2, but also change some things. This is obviously the case with Niotron, because they use a different source code for the File component (than it is currently implemented on the AI2 test server).
Oh i see well that's makes sense. Well then i got my coffee time to wait I guess....
Other commercial builders, some functions are paid. Also, these builders are focused on building commercial apps that are placed in the Google store. Therefore, a quick update is important there.
AppInventor is a platform primarily for learning. The MIT team does not put the publishing of apps on the Google Store first, as it is not very much needed when learning to code.
@Anke
I tried niotron and saw that, there also exist requestLegacyExternalStorage=true in niotron builder.
According to my problem (google said), Is it safe to use sdk 30. Please explain in details if possible.
