I've just recently come across this question, as I have been struggling with the same problem.
I have a potential solution which I've found which might help others. These instructions are for a Samsung Phone, but you may be able to find the equivalent options on Android.
I have a device that requires me to connect my phone to it via it's own hotspot. The hotspot the device creates doesn't have internet access, and because my cellphone thinks it is connected to a wifi network, it then refuses to use mobile data. I only want to use mobile data when connected to this ssid.
These are the steps I used which seemed to work:
- Activate hotspot on device which does not have internet access.
- In the connection settings connect to device.
- Android then prompts you saying the current network does not have internet access.
Connect just this time Always Connect Disconnect
IGNORE THIS PROMPT! Close the wifi connection app, and you should now have both a mobile connection and the network connection.
Note: If you have already accepted one of these options, you can either:
- forget the network, and try this again,
- otherwise go to
Connections -> Wifi -> Advanced -> Switch to mobile data -> Network Exceptions and delete the entry for the SSID in question.
