Perhaps the EU can step in and force these SoC companies to change their way of working so that a user can simply install Android 17 with a few clicks regardless of their hardware (to a point). Like how desktop computers work.
Mobile chips are not used for desktop and servers, not used for Windows and Linux. They are used for Android, and that's a 98% of the market. The customers of the chips (the companies which develop devices on the chips) just don't use Windows or Linux, that's why there's no reason for a chip company to support it.
Android does not use desktop/server firmware, desktop/server bootloader, and even desktop/server stock Linux kernel. They have their own Generic Kernel Image with the Android patches on top, strict Google requirements for the booting and working process, etc.
PC operating systems are supplied by third parties that are not part of the computer manufacturer, motherboard or processor vendor. All component manufacturers must write drivers for Windows, certify them with Microsoft, and make sure that their device works properly ideally on any computer. You, the user, buy (or obtain) a copy of the operating system from the operating system company.
The operating system for a appliance (smartphone) comes with the appliance itself (as a bundle), and is supplied by the appliance manufacturer, not by operating system manufacturer. The manufacturer of electronic components does not need to contact the creators of the operating systems, they write a driver for Android kernel (yes, for Android kernel, with all its wakelock subsystems and such in mind) and gives it to the manufacturer of the appliance directly (and sometimes only supplies hardware, and the driver must be made by the manufacturer of the appliance).
Fairphone chose to use T2Mobile as their ODM designing and making their devices. They chose to use the SoC platforms they did. They chose to focus very little on providing updates to the point that the Fairphone 5 and earlier have an end-of-life Linux kernel without security support. Fairphone 5 is still presented as supported with many years to come but it's not getting a large portion of the high importance security patches anymore.