No OS is perfect, as you likely do have to use a proprietary modem and some proprietary apps, but CalyxOS works well for me on my Fairphone 4. I like the base install being as free as realistically possible on a modern Android phone, especially replacing Google apps with microG. Just don’t enable SafetyNet if you don’t want it to run (sandboxed) Google blobs. That API is deprecated anyways.
The experience is smooth, free and I get a repairable phone without having generative “”“AI”“” shoved down my throat. A win on all fronts in my opinion.