Firmware updates are expected to be available here: https://www.expert-sleepers.co.uk/es9firmware.html.
However, beta versions tend to appear elsewhere. For example, the 1.2.0.beta versions were in this thread: https://modwiggler.com/forum/viewtopic.php?f=35&t=226245&start=225#p3413903.
Committing them here to sort of keep track.