Additionally, regarding Fairphone Open OS for the Fairphone 3/3+ they say “For Fairphone 2, we offered Fairphone Open, an OS with no Google services pre-installed. Fairphone Open will NOT work on the FP3/FP3+.”.
For the Fairphone 4 however, they say “In the past, we offered Fairphone Open for our devices. Fairphone Open is an OS without pre-installed Google services. Unfortunately, you will not be able to run Fairphone Open OS on your Fairphone 4. Yet.” ← Yet 