Can't view desktop version from mobile (iPhone)

Sometimes the GitHub mobile app is missing features that exist on the desktop version of github dot com, and the mobile site of github dot com is also missing these features.
In these cases it would be nice to be able to “Request Desktop Site” within a mobile browser on the iPhone visiting github dot com and use some features that are missing or in unfamiliar places on the alternatives (on the GitHub iOS app and the mobile version of github dot com).

However, “Request Desktop Site” for does not work on any major iOS browser. I have tried, Firefox, Safari, Chrome, Opera and Edge.

Please could the “Request Desktop Site” feature actually be respected by It works fine on many other sites.