My WIFI internet is very slow. I would like to use my mobile internet of my phone, but connect to my wifi because it has Google Cast in it.
Phone: Oneplus 2
OS: OO 3.1
There should be an option called Smart network switch which switches to mobile data connection whenever the WiFi connectivity is limited or unstable.
The screenshot below is from Samsung Galaxy.
Actually you can do it on Android, just a bit of imagination and effort:
I just made an adaptation from this post. I never tested it myself, but SHOULD work. Just give it a try.
The snapshots are from Samsung Galaxy on Marshmallow (6.0.1). It may be different on other phone model/Android version.
Chat with OO support
After reviewing the link you provided and checking the current features running through the OnePlus Phones, we currently don't have this right now however will be able to raise this over to our developers team to check if this is possible in the near future.
There is no such feature in OO as in Android shown here
No imagination can do a work which does not exist.