Download Android 10 stock firmware PC version for Tanix TX6S TV Box from here, here or here. Download Android 10 stock firmware OTA / Local update version from here. Flash it from PC using LiveSuit v1.11 or from SD card using PhoenixCard v3.09.
Archive name: TX6S-4G-20200220
Archive file size: 722 MB
Model: Tanix TX6S TV Box
Platform: Allwinner H616
Caution Please do not update firmware unless you know what you are doing, you really want it or it is absolutely necessary. Firmware updates may occasionally have bad results, like bricking your device, temporarily or permanently. The firmware update process is done entirely at your own risk. Before attempting to update the firmware, back up your data.