Multiple networks simultaneously

I have a wireless sensor (A) that sends the captured data to an Android device (B) over a wifi network created by A. The data is received correctly on an app running on B, however the problem is that the wifi created by A lacks internet and I need to maintain internet connection on device B. From the information I have been able to find, Speedify could accomplish this task, however I need a free alternative. The objective is that B can have internet while using the data reception application that needs to be connected to A's Wi-Fi, perhaps there is some way to force only the application to connect to A's Wi-Fi ( as a possible alternative to the simultaneous use of networks). Device B would have the possibility of being rooted if this were necessary. Related question: https://stackoverflow.com/questions/77288629/how-to-route-local-traffic-over-wifi-and-everything-else-using-the-mobile-data-i