As @Incanus says Paranoid Android is obviously Android and the alternatives /e/ and Lineage are also Android.
AOSP Android Open Source Project is the base OS from which all the above are derived.
I doubt you will find a non Android based OS that will work on the Fairphone or any other ‘Android’ phone
So the alternatives mentioned by @Incanus are about the best you are going to get.
However you can use Android without a lot of Google which is more what the alternatives are about.
I don’t need a google account, have disabled as much google apps as I can and could use the debloater options. I’m not paranoid but just can’t be bothered to support the google data gathering to the degree they would like, it’s just feels to demanding. So I presently use the stock Fairphone OS.