I've had a Fairphone 4 running CalyxOS for years. I'm very happy with it.
I really like CalyxOS' firewall app.
I would run GrapheneOS on the Fairphone. But the project stupidly decided to stick to Pixel phones for "purity" reasons, instead of recognizing that not everybody has threat models that require security cranked up to the max - not to mention, not everybody is cool with giving Google money or owning Google hardware. And now Google is pulling the rug from under them. Too bad...