Official support for the S805 chip ended years ago, so most available links point to community-driven projects.
: This forum hosts a popular Android 5.1.1 "Lollipop" custom ROM by developer for the m201/S805 chipset on 4PDA's MXQ S85 page ChinaGadgetsReviews mxq s805 firmware 51 download link
The search for the "MXQ S805 Firmware 51" is less of a technical query and more of a ghost story among the hobbyist community. It represents the "Holy Grail" of bricked TV boxes—a version whispered about in old forums that supposedly unlocked hidden hardware potential or fixed the infamous red-light-of-death, but the link is always dead. The Ghost in the Box Official support for the S805 chip ended years
If WiFi won't turn on after the update, your box likely has a different WiFi chip (like the RTL8723). You will need to find a firmware version specifically labeled with your WiFi chip's model number. The Ghost in the Box If WiFi won't
Considered a safer alternative to Android for users mainly wanting to run Kodi. Supports dual-boot from an SD card. Stock Firmware: Official builds like KOT49H.20151225 are more stable for basic media use. Installation & Download Resources
Firmware 51 for the MXQ S805 is a "stability patch." It does not offer new apps or modern Android features, but it is the best firmware if you are trying to revive an old box for use as a lightweight media player (using local files via VLC) or a retro gaming emulator
: For a smoother experience on older hardware, many users prefer AlexELEC, which can be found through the MXQProject Stock Firmware (Google Groups Archive)