Regarding my question about keeping my copper phone lines or not, I just saw this which I'd missed before; AT&T has announced it intends to get rid of its copper networks by 2029, assuming regulators allow that. California might be an exception.
https://www.pcmag.com/news/att-to-retire-traditional-landlines-by-2029-except-in-this-state
In 2024, California said no to its request to get out of its Carrier of Last Resort obligations.
https://www.cpuc.ca.gov/news-and-updates/all-news/cpuc-rejects-att-request-to-withdraw-as-carrier.
But it's trying again:
https://www.ptreyeslight.com/news/landlines-endangered-by-rule-update/