Instead of software versions, the D-808 is categorized by physical manufacturing updates:
If you need improved media compatibility or fixes and can obtain a verified firmware for your exact D-808 revision, the update is worthwhile; otherwise, weigh the risk of bricking and data loss. Follow the checklist and prefer official/verified community sources. xhdata d-808 firmware update
After extensive research across the following sources, no official firmware update file has ever been released: Instead of software versions, the D-808 is categorized