I am not sure which elements are at play with the issues I am facing so I have tried to give a fairly wide outline.
We recently deployed a company SPA web application for an annual event that was based on ASP.NET MVC 5 with client-side JavaScript and jQuery. It used Windows Authentication and staff could access on a mobile phone.
The basic functionality was search for a contact, enter forms data and submit updates. After initial page load, all requests were handled using AJAX requests e.g. $.get(urlToGetContacts).done(funcHandleDone).fail(funcHandleFail)
We tested in the desktop browser before deploying to externally accessible sites so that we could test using mobiles.
We couldn't "break it" using our own phones (a mix of various Android and iPhone), however, many staff used Company mobiles (iPhone SE 3rd Gen, forcing the user to use MS Edge browser).
There were some weird bugs exclusively with these (even though I have an iPhone SE 2nd Gen with same iOS version and the same Edge browser and build number and it was totally fine).
Firstly, there was the display - the flow of the text and graphics were different - more clunky with the company mobile.
However, more concerning were issues with searching for contacts which would not return back and users were stuck in a loading state. No server side errors were generated.
I have been told we are using Microsoft Intune to manage the company iPhone fleet.
The question is where could these issues be rooted?
How would you diagnose them?
For next year's app I am wondering on whether we would be better off deploying a .NET MAUI app.
You haven't made the problem very clear, but if you only want to hear advice for troubleshooting, you first need to figure out if it is caused by Intune or not.
Find an Intune-managed device and exclude this device from Intune for a test. Or add a new device (that shows no problem before) to Intune and monitor the behavior.
If you can confirm Intune caused this issue, then try removing some of the (browser) policies until everything works fine again. If Intune has nothing to do, then try different browsers to check if it is caused by browser or the device itself.