They what and what?? Generally the Omada-stack devices are just on-premises hardware that you control. If you enable automatic firmware updates, then yeah, “if they push a bad update” and all (similar to a Linux distro with auto updates enabled). To improve operations, and enable certain features, there is the “cloud-based controller” software (appliance), which is named weirdly, because it generally does not live in the cloud - you can self-host on-premises, though its core software component is a black box and not (F)OSS (also available as an actual hardware appliance). There have been instances of the devices “phoning home”, though you might be able to limit that to some extent with firewall rules.

Just very quickly: the books are so much better than the show! I had to stop watching the show somewhere I think in season 2 - everything started digressing/simplifying too much from the books (the characters became flat and uninteresting etc.) So yeah, I found the books much more enjoyable.