You can install Windows 10 ARM on Lumia 950/XL using WoA-Installer tool
Since last year, there have been developers in countries to try to bring Windows 10 ARM to Windows Phone devices. Of course, the root cause of the magic change is that Microsoft has completely abandoned the Windows Phone system.
The good news is that the work of these developers ended up with very interesting results, the Lumia 950 series successfully runs the Windows 10 on ARM special edition. The better news is that not only does the Windows 10 on ARM special edition run successfully, but most of the features are still normal and can even be used.
Windows 10 on ARM itself is not developed for smartphones, but Windows 10 can be adaptively displayed on different screens. The screen size is small, so the entire Windows 10 interface is also reduced, and each menu can be displayed in a folded manner, even for basic use.
In theory, users can use the UWP application that supports the mobile phone directly from the app store after running the Windows 10 on ARM version. Some UWP apps are not optimized for small screen devices such as mobile phones, so the display is a bit weird, but many popular applications are still compatible. So you can only say that users who want to run Windows 10 ARM on their own Lumia 950 series and try it out. Of course, it is risky if it is bricked.
You can click here to view the tutorial and download the various tools.