Problem: If I look at the documentation for any integration I can see its IoT class. If that class is “Local Polling” or “Local Push” I would assume that the device works fine even without the cloud. However, this is not the case. HA can still talk to these devices even if the cloud is down but the device may not work at all. This confusion is further amplified by cloud icon on the HA frontend. As a user I would assume any integration and device that does not have that cloud icon to still work even if there is no internet available.
Example: If you block the Nuki bridge (Nuki - Home Assistant) from the internet it works fine for a couple of hours but if you restart home assistant after a given time period and it tries to re-authenticate with the bridge the bridge rejects any authentication until cloud access is restored. Meaning you would be unable to unlock the door which could lead to serious problems.
Proposed Solution: Add an additional indicator and/or a list of devices for each integration that communicates clearly if a device will work in an internet free environment.