I'm thinking of getting a fairphone in the future. I like that they are modular and last a while. Are they easily customizable to where I can flash a different ROM? Is the default configuration private?
The default is Fairphone OS. It is Google Android but they don't pay to license the name 'Android', so they have to use an alternative name.
You can install /e/OS (even preinstalled by Murena) or DivestOS. Any other option doesn't make sense as Divest is best in terms of security and privacy among all available custom roms and /e/ is most convenient (good but not perfect privacy, bad security but with MicroG, relock and App Lounge as well as Murena Cloud)