@TEH
You don't port Ubuntu Touch to a chip, but to a phone with full hardware around a particular chip.
This means that a port for a phone with one particular chip, will not work on another with the same chip but different peripheral hardware.

Plus, don't choose any old phone that would not support Ubuntu Touch 20.04 and further, it must be a phone that got an android rom that includes a recent Linux kernel.

For now I'll move your topic to general forum section, as porting section is for ongoing ports.

You should take a look and seek for help understanding porting effort at UBports porting telegram group to figure out what can be done depending on which hardware you choose.

BTW Qualcomm chips based phones can get UT working on it, that's the cas of Fairphones for instance.