Your effort here brings up a sort-of related question. I could see using the IOBroker on a Pi (pulling in other devices on my boat as well), and then wanting to connect to it with my cell. The issue, that I've been trying to solve, is this.
If you connect your cell phone to an AP (the SMBS0, or a Pi running IOBroker), then the cell won't access the internet through cell data. This means that I have to keep connecting/disconnecting frm the AP. I think that the fundamental problem is that a client cannot be on two networks at once -- if you type an IP address, it can't figure out which network you mean.
Note, there is a feature on Android to say "if the WiFi has no internet, use cell data." This actually works -- it determines the WiFi connection has no internet so it "ignores" the WiFi connection and uses cell data -- but since it ignores the WiFi, it can't access the WiFi.
Has anyone found a way to connect to an isolated AP (no inherent internet) while also maintaining Cell data to the internet?