There are some more traditional home phones which work on 4/5G networks with a DECT handset which talks to a cellular base station. You might look into switching to that model to replace your "cell phone as a home phone" concept. It makes it a bit easier to add another handset to the DECT network and often means convenient cradles to charge the handsets while the base station stays in a good signal spot with plenty of power.

Just a thought when it comes time to change out that device.