If you are interested in alternative OS, consider:
- /e/ OS, a new Android 10 version that supports Fp3+ in underway, https://www.fairphone.com/en/2020/04/30/keeping-your-data-safe-with-e-os/
- the up-coming Lineage OS release [ROM][UNOFFICIAL] LineageOS 16.0 for FP3
- [HOW TO] Flash a custom ROM on FP3 with GSI