@justine for PostmarketOS its not very viable for daily driving right now. The Farphone 5 dies not have earpiece support, so calling does work but only with speakers and external audio like Bluetooth (from what I remember, I'm not sure about Bluetooth but I think it would work). And switching audio sources doesn't work during calls.
Android app support is also flakey. To be fair haven't tried it with a device with more ram and power like the Fairphone 5. Only tried with a pixel 3a. There is also work going on to port the proprietary Aliendalvik android app support to postmarketOS.
But anyway if you want a phone with better audio support and calling the Oneplus 6 / 6T are good. Thats the one that has most support now. But the Fairphone 5 has made a lot of progress so its not very unrealistic to think it will get more progress.
There is also security. For data harvesting you don't really have to worry much of course, it being Linux. But physical hardware attacks are more of a danger, like someone using SSH.