Hi,
You are right. I have a trusted network with Ethernet/WIFI 5GHz and an untrusted network with WIFI 2,4Ghz. There is no connexion between the 2 network (except if I accept the connexion).
Of course, if you want to connect on WIFI 2,4Ghz, you can (but this is your problem and i can see your login/password). In the protocol WIFI, there is no obligation to have a password. The only problem is the french law.
My domoticz server is on the safety network. So, i accept a connexion http from server to Shelly and of course, the answer. All the (chineese) device can do everything on internet, I don't care