I run a flat /21 network for organizational purposes. Hubitat works fine with it. The key is to get the netmask correct in Hubitat. The following should work while keeping the hub IP as DHCP, but you'll get a 'Missing IP' error.
http:///hub/advanced/switchToStaticIp?netmask=255.255.252.0
[Update - see message further below]
I'd request a feature that all these 'hidden' network settings be added to the UI, behind some sort of 'advanced' warning that Hubitat uses in a couple other places. Almost all consumer stuff that has network settings includes a UI configurable network mask. It seemed to be on the list at some point.
Or at least get all the endpoints added to the documentation instead of pointing to community threads. @bertabcd1234
