Is UT in PinePhone same thing than in another phone?

[bcnaz]

I discovered Linux phones by finding pinephone. However, I see that UT has been before than PinePhone. So, if UT is installed on another phone (e.g. Oneplus one)  is that already a Linux phone? Or does it still need some android software?

If so, what makes PP so special? or it isn't?

Is anyone kind enough to share some thoughts?

thanks!

Rob Braxman on YouTube goes into great detail describing both pure Linux phones and phones converted to Linux.
It would take many pages to describe them.