Moral of the story:
S9 owners DO NOT upgrade firmware to 2019 version, you will lose SSH access!!!I wrote that for a reason. Still, you could use an SD card to flash it back using that convoluted T9 firmware method, or simply boot
Braiins OS and install that instead.
I don't think S9s should be running any other firmware at this point, unless you have the ancient controller.
With Braiins OS you can improve the efficiency from 100w per tera hash down to around 80w. This alone increased the lifetime of the units against Bitmain's wishes, which is why they responded by locking down ssh access since 2019.