Back in December 2019, Microsoft finally killed off Windows 10 Phone as it announced the end of support. The company's grand plans with Lumia and Windows Phones sadly never became the success it needed to be in order to be able to compete with the likes of Android or iOS.
Thus Windows 11 Phone never became a real official thing outside of concepts. However, there is a free unofficial way that makes it possible, albeit the experience may not totally be free from flaws. Dubbed Project Renegade, the mod enables users to try Windows 11 on Qualcomm Snapdragon phones, among other devices.
WIndows 11 on budget mobile phone using Renegade Project
Using that, a Reddit user anh0l managed to run Windows 11 on their phone. They write:
For a couple days i wanted to install windows 11 on my old phone cuz why not. Also, i did have experience in running linux distro (postmarket os) on my different phone so i thought it will be not more difficult than that. I was mistaken.. it took me around 8 hrs of trying and finding tools and files that could work on my device (Mi POCO X3 pro). But finally, after 3 attempts i managed to get it running pretty smooth. Only thing, touchscreen it kinda messed up and inverted by half..
As you can see, they say the experience went mostly great barring some issues with the touchscreen. What's great is that the OS was installed on a rather inexpensive device, the Xiaomi POCO X3 Pro, which costs around $250-300.
In case you are wondering, the Renegade Project is an EDK2-based UEFI firmware and has been tested and verified to work on various devices including the MI POCO X3 Pro. In the case of Microsoft, the Nokia Lumia models 950 and 950 XL are supported too, as well as the Surface Duo and Duo 2. You can find the full list of supported devices on this page on the project's official website.
The website also has an in-depth guide on how to go about the project which you can find on this page. The author has advised to stay away from lightweight Windows 11 versions as they are stripped down and can cause compatibility problems.