Window 10 Mobile may no longer be supported, but that does not mean you have to retire your Lumia 950 or 950 XL.
Developer José Manuel Nieto has created a tool which makes it super-easy to install Windows 10 for ARM on your Lumia 950 or 950 XL, meaning in theory you should be able to run any win32 app on your handset.
You will first need to unlock your handset using WPInternals, then, while your phone is connected to your PC, download Windows 10 ARM64 image, WoA installer and core packages. After downloading the files, run the tool, import core packages from the advanced settings, and follow the on-screen instructions to boot the OS on your phone.
As can be seen from the screenshot, both dual-boot and single-OS options are available for the install.
Of course it is fair to ask what you will do with full Windows 10 on your phone, but in the end, was this not the eventual holy grail of Windows 10 Mobile?