Actually i looking exactly for the opposite case:
Is there a way i can prevent the frontend-user from selecting the upload function or let the user just choose from the media-gallery. Like preselecting the tab media-upload. Any hints?
So, i found the solution by myself:
It’s actually the argument “uploader” for the acf_form function. I had it on ‘basic’. Instead you wanna change this to ‘wp’.
Problem solved