I do not own an apple device, so I only noticed this problem at a recent convention, when I had someone load a page that contains an iframe embed of one of my virtual tours, using an ipad. This problem is not present on Chrome on Android, but it is present in the DuckDuckGo browser on Android (which I'm currently using for testing).
I recently solved a similar problem that WAS present on Chrome on Android... there was an update to chromium that blocked mobile sensor access, resulting in the removal of the VR and gyro buttons from my embedded vtours (embedded using iframes). The solution that I found was two parts:
1. all data had to originate from secure locations (https)
2. I had to add updated tags to my iframe
I thought this had solved the problem (because it was fixed on Android), but now I know that the ability to toggle fullscreen is still missing from some mobile browsers.
Here is my iframe after solving that chromium update problem:
<iframe src="https://www.tinynestproject.com/explore/zyl-vardos/damselfly/" width="100%" height="320" allow="fullscreen; gyroscope; accelerometer; magnetometer; vr; xr"></iframe>
And here is my iframe after much effort to brute-force the allowing of fullscreen:
<iframe src="https://www.tinynestproject.com/explore/zyl-vardos/damselfly/" width="100%" height="320" allow="fullscreen; gyroscope; accelerometer; magnetometer; vr; xr" allowfullscreen webkitallowfullscreen mozallowfullscreen allowvr="true" allowfullscreen="true"></iframe>
none of the following would enable the fullscreen button in DuckDuckGo:
allow="fullscreen"
allowfullscreen
webkitallowfullscreen
mozallowfullscreen
allowfullscreen="true"
allowfullscreen="yes"
Banging my head against a wall here... what is preventing fullscreen from working? VR and gyro seem to work, which require access to the device's sensors...
Here is my testing page -> https://www.tinynestproject.com/explore/demo/