As a former polyamoric person, here’s how I (still) think of it: You can’t control your feelings (they are merely physical reactions to situations) but you can control how you deal with them. Or how you act on them.
So in a sense, in my opinion, you’re both correct.
I have! I tried it over a year ago, and LTE wasn’t working so I gave up. According to this it’s still not functioning :( https://wiki.postmarketos.org/wiki/Fairphone_4_(fairphone-fp4)