A lot of owners of Lumia smartphones would like to play Pokemon Go together with iPhone and Android friends. Unfortunately, Niantic studio did not prepare the version for this niche mobile operating system. I think that only old BlackBerry OS has worse situation.
Of course, Windows Phone users have written a petition to Niantic studio, but it is hard to say if they react on this. In the mean time, some Windows Phone developer has decided to create a 3rd party port for disadvantaged Windows Phone users. However, this 3rd party game does not look the same as the original Pokemon Go game.
The 3rd party Pokemon Go client for Windows Phone does not provide AR (Augmented Reality) feature.
The developer says that this 3rd party client will give Windows Phone users “the ability to play in the same game-world as your friends that are playing with an Android or iOS device”. In order to lunch the game on you Lumia (or other Windows 10 smartphone) you have to have Pokemon Trainer Club account. However, you can use Bluestacks service for this. The installation instruction is available on GitHub site. Developer provides two installation ways (for beginner and expert). However, if you are not a Windows Phone developer, then you should follow the instruction for beginners. If you have any problem, you can ask the developer for help on RedDit site.
There is also a question how long this 3rd party client will work.
We all know that Niantic does not like 3rd party tools. This is obvious, because people use these tools for cheating. For an example, they try to use Fake GPS tools in order to move to any location. Very interesting is also fact, that PokeVision service has stopped working yesterday just after v0.3.1 update. People were using this site to track Nintendo animals in their area. This site was very useful, because tracking mechanism built in the Pokemon Go game, does not work. I think that Niantic studio will close their API in the near future. However, I hope that they will also port iOS version of Pokemon Go game to Windows 10 platform. I bet that Microsoft will help them to achieve this.