I have noticed that pulldown menus and people picker fields are working differently now on mobile devices. Instead of the menu dropping down, as it does when runnit it in chrome on a PC, it fills the screen with the selectable options. On android, it works, but on apple devices, the screen that pops us is empty, so nothing can be selected.
Which data source do you used in your app? A SQL Table?
Based on the issue that you mentioned, I have made a test on my side, and don't have the issue that you mentioned. Please check if the version of PowerApps Mobile App in your iOS device is the latest version, if not, please consider upgrade it to the latest version, then run your app again, check if the issue is solved.
Also please consider turn off the "Improved app rendering (final validation)" option and "Explicit column selection" option within Advanced settings of App settings of your app, then re-publish your app, then check if the issue is solved.
If the issue still exists, please consider change the "Allow selection of" property to "People and Groups" option as below:
then re-create a new connection to the SP List from your app (remove the old SP List connection), then re-publish your app, check if the issue is fixed.
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.