If you're unfamiliar with it, there's an entire community of users that love to figure out how to install an OS on a phone that's not supposed to be there. It would seem that the harder it is to do, the better, as enthusiasts simply can't resist.
Most recently, we saw Windows 10 get installed on a Lumia 830, and Windows RT installed on a Lumia 950. Today, Twitter user @imbushuo posted images of Windows RT 8.1 running on a Microsoft Lumia 640 XL.
The user, named Ben, promises to publish notes in a few days, showing off how to install the OS on a device.
Of course, none of this means anything to the average end user. We love to check these things out because frankly, it's just cool.
The next step would be to see if screen mirroring works, either wired or wirelessly. If that's the case, then it's feasible for the device to be used as a low-powered PC when connected to the monitor. After all, Windows RT did offer nearly full-featured versions of Office 2013, along with some Windows Store apps.
Ben seems to have been working on getting this going for days, so presumably, there will be more details moving forward. We'll be looking forward to seeing his notes.