@arubislander Thanks for the clear answer.
So, I hope for a future with smartphones whose hardware and drivers are open.

Hello,

I am the owner of an Aquaris E4.5 Ubuntu edition, purchased upon its release. I used it for 2 years with Ubuntu Touch, and then, when Canonical discontinued support, I switched to Android for 2 years before changing phones.

A few weeks ago, I reinstalled Ubuntu Touch on my "old" Aquaris E4.5. I was pleasantly surprised by its smooth performance. I also take this opportunity to thank all the people working on this project.

I also noticed that my Aquaris E4.5 will not be updated to 20.04 (or newer), and I regret that.

I am considering changing phones soon and would like to understand the compatibility of a device and the lifecycle of a phone under Ubuntu Touch. Clearly, installing Ubuntu Touch is very different from installing regular Ubuntu on a PC. Ubuntu Touch cannot be installed on all devices, and older devices cannot always be updated. (For example, Aquaris E4.5 runs on 16.04 but not on 20.04).

I would like to know what makes a phone compatible with Ubuntu Touch?

I would also like to know how to determine if a device that is compatible with 16.04 or 20.04 will be compatible with 22.04 or 24.04, or even beyond (What is its lifespan)?

Lastly, in the case of the Aquaris E4.5, I understood that it couldn't be updated to 20.04 because the kernel was too old(I read that on another post), but why is it not always possible to update the kernel?