@jnm I'm a bit late in the discussion but what I can say is that I have the exact same problem.
I also use a sim from Free Mobile.
Here are additional information :
- When data stops working, flip airplane mode ON then OFF. You get data again for some (undefined) time.
- With some combination of WIFI ON / WIFI OFF / DATA OFF / DATA ON / AIRPLANE MODE ON / AIRPLANE MODE OFF, at some point, I get a stable data connection. I have not found the gold sequence. Maybe timings are of importance here. Once data is stable, I can switch data OFF then ON without any problem... Until I activate WIFI. Then the problem rise again.
Or maybe I'm completely wrong. Maybe data works when the network used is from another operator (roaming). Is there a way to know which operator is really used in UBports ?
My feeling is that this is a software issue, not an operator issue. My feeling is the connection is established but the system says it is not. Again, I can be completely wrong.
@jnm, you said there were no problem before end of 2023. Free has activated VoLTE and VoWIFI on their network at that time. Maybe this is the source of the issue...