And nor will they work during a power cut. Work of the devil if you ask me.
For those that really need it - which includes a lot of remote telemetry solutions - can use something that appears like a normal landline (its converted to VoIP at the exchange) until the end of the decade. But beyond that is unclear, sounds like BT have given notice that people need to sort their shit, including battery backups for vulnerable users*, alarm companies pull their fingers out, and telemetry solution users to move to something from this millennium.
*Back in the day, to get approval, cordless phones either had to be secondary devices, or had to come with a battery backup unit. But over time, although I don't think the approval rules changed, everyone got cordless phones as primary phones, and got shitty when they stopped in power cuts