I have not tried anything yet tbh as I have not got the S9J.
I have in the past tried swapping s9 and S9i boards but the heat sinks are physically are different height so not compatible.
I presume BrainsOS is on their site somewhere and each model of S9 has its own FW version?
Thanks
yes and no
braiins has the firmware on their website and does not have multiple s9 firmware they have one exclusive firmware for most every s9