Until now, marking a field as "Read Only" in the aprx (Data Design > Fields > check the Read Only box) worked great. Any published maps used in Portal Web Maps, Field Maps, Web Mapping Applications, etc, honoured that setting.
Today I learned that Instant Apps do not honour that setting (we are running 11.3). I used a published feature layer as usual, whose InfrastructureID field was marked "Read Only" in the aprx. However, in my Sidebar Instant App, the field was still editable. I tested editing it and saved, and my changes saved.
After some Googling I learned you can make changes in the Web Map in Portal, by clicking the layer in the layer list, then clicking the "Forms" widget. Start configuring a form for the layer -- click "Convert pop-up" to begin. Then select the field (in my case, InfrastructureID) and scroll down on the right side until you get to the "Logic" section where you can uncheck the "Editable" box. You have to repeat this for every layer and every field in your web map that you want to be Read Only.
Idea: It would make more sense for any fields that are marked Read Only in the aprx to default to non-editable, and then optionally users can use this forms setting to enable editing if they want to override it.
