Install the Adapt firmware updater on MiSTer by downloading reflex_updater.sh and copying it to the Scripts folder on your SD card.
Alternatively, add the following to your downloader.ini file to install and auto-update through Downloader and Update All:
[misteraddons/reflexadapt]
db_url = https://github.com/misteraddons/Reflex-Adapt/releases/latest/download/reflexadapt.json
The reflex_updater.sh script can then be launched from the Scripts menu.