There is a well known "bug" when working with SharePoint list Yes/No column :
The Yes/No value can not be compare to boolean type true/false.
Filter(SPList,YesNoColumn = true) will not return all the items with a Yes value .
The workaround is to use 1 or 0:
Filter(SPList,YesNoColumn = 1)
This will return all items with a true value, but the designer shows an error because we are comparing a boolean to a number.
It would be great to fixe that, as a Yes/No column is indeed a boolean value, we need to be able to compare that to a boolean value in PowerApps.
Théo
Adding @GregLi as an FYI.