How private is a fairphone?

The stock Fairphone runs the stock full-blown Google spyware stack. Privacy isn't Fairphone's selling point: it's repairability.

You can install CalyxOS very easily on it however. That's what I'm rocking on my Fairphone 4, and it's great. I have no issues with it.

As others said, it's pretty stock android so... Bad. But you can buy it from Murena pre-flashed with e/os and then have a stock phone with a locked bootloader running a decently private OS. The bootloader is unlockable if you so wish.

I know that for a fact that you can't install GrapheneOS on it, but CalyxIS is available for the Fairphone, then flash that and you'll have full protection, minus mandatory communication services that are require to use any kind of a smartphone.

I think the normal fairphone is just stock android.

There is a "Murena" version of it sold by Murena that comes with e/os preinstalled, which is based on android and works with some android apps.

The default Android on them is pretty standard including Google Play services, so it is not great in regards to privacy (but could be worse, like an Apple device or so).

But for most of their models you can find good alternative Android roms or even mobile Linux distributions like PostmarketOS.