As an alternative solution, you could consider take a try to save your SP list records into a Collection (if the number of your SP List records is not more than 2000), then use the Collection as a data source within your app. I have made a test on my side, please take a try with the following workaround:
Set the OnVisible property of the first screen of your app to following:
On your side, you should type:
Set the Items property of the Galleryto following:
Filter(RecordsCollecion, Flagged <> true)
Community Support Team _ Kris Dai If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.