The Linux-sunxi.org project is the holy grail for Allwinner devices. While they focus on mainline Linux, their wiki provides generic sun50iw9p1 board detection and links to factory firmware dumps.
Primarily the Allwinner H616 (Quad-core A53 with Mali-G31 MP2 GPU). Where to Download sun50iw9p1 Firmware for Free sun50iw9p1 firmware free
Surprisingly, many developers upload stock images or flash tools here to help users unbrick devices for free. Search sun50iw9p1 PhoenixSuit . The Linux-sunxi
Modifying firmware voids warranties. Ensure you have the legal right to modify your device under local regulations (notably EU right-to-repair laws). The author is not responsible for hardware damage. Always verify checksums (SHA256) of downloaded firmware using certutil -hashfile yourfile.img SHA256 to prevent malware injection. Where to Download sun50iw9p1 Firmware for Free Surprisingly,
Select to perform a clean installation, erasing all old system errors and user data.
— but you may need to move away from the vendor Android image. The best free (as in freedom) option today is Armbian + mainline Linux , even if it requires a bit of tinkering.