HTTP Request: select if to use WiFi or Data

It would be very useful for me to have a way how to force s HTTP request to be routed using the WiFi connection. Especially when the system is using mobile data and I join a WiFi network which requires login in captive portal. I have a task which does this, but when i have my cellular data active this request is just sent using the LTE connection.

Alternatively there could be some option to handle Sign-In portals, but that seems to be even more work.