The flashing method depends on the firmware file format. Use the appropriate tool for the format you downloaded.
Community projects like MXQ PROJECT offer guides and unofficial firmware links. Firmware Type Source / Resource MXQ S805 Lollipop Installation Often based on the "Abdul" port for K1 boxes. LibreELEC / AlexELEC AlexELEC S805 Update Guide
The digital trail usually leads to a 2016 thread on a now-defunct hobbyist forum. The legend goes like this: a user named ElectronVolt posted a link to "Firmware 51," claiming it was a custom kernel that bypassed the S805’s thermal throttling and allowed for smooth 4K playback—something the hardware wasn't technically meant to handle. mxq s805 firmware 51 download link
: Custom ports, often adapted from similar hardware like the K1 box or Minix Neo X6 , allow the to run Android 5.1 . Common Firmware and Installation Resources
Insert a non-metallic toothpick or a paperclip into the AV jack on the back of the MXQ box. Press and hold down the hidden button inside. The flashing method depends on the firmware file format
While there is no official Android 5.1 (Lollipop) release from the original manufacturer for the
: A comprehensive list of stock and custom ROMs (including versions like 107k, 108k, and 110k) can be found in the community forums at Alternative OS : For better performance, many users switch to (Kodi-based OS), which are maintained for the S805 chip at rigacci.org Key Feature: Material Design & Better Notifications Firmware Type Source / Resource MXQ S805 Lollipop
Official support for the S805 chip ended years ago, so most available links point to community-driven projects.