Hi,
The fact that you did not find an working example is that there isn't any.
There are a lot of discussions though, explaining why that is.
Currently you may have simulations of nodes with two interfaces (WiFi & LTE) but the two systems are NOT integrated.
You could for example have MP-TCP or SCTP (with the aid of DCE) to simulate multi-homing, but no vertical handover.
In order to have vertical handover, there are a lot of missing components.
Regards,
K.