Ah. Terminology. A landline is just that a line that is run across land to a telephone exchange.
"Digital Voice", "Internet Calls" etc are VoIP although they are fixed by use of a router location to which you can then connect analogue (all) or digital equipment (BT). The generic term being used is Digital Voice.
We haven't really moved on in the last couple of years. As always its commercials winning over technology.
Cheapest UK voice option is still a Unlimited Calls and Text SIM from someone like ASDA.
- Use a basic 4G cradle phone as a cordless handset. eg .
Easyfone Prime-A6 Sim-Free Easy-to-Use 4G Mobile Phone for Seniors or equivalent just ensure it does VoLTE.
- For corded phone or your own DECT Handsets use a basic VoLTE router such as the Alcatel HH71V1 (cheap on ebay) with a SIM that also has a small data allowance. VoLTE router can be positioned where the signal is best with extension wiring to phone(s).
However as you have poor 4G reception and appear to have already dumped the landline all you can do is compare the main VoIP suppliers and look at their T&C detail for you use pattern. Most have call plans based on business use.
My advice to others is that if your are likely to make a lot of calls, or i/c only, people should not simply dismiss the major players. VM and Sky include a DV line without cost/price and hence are ideal for incoming and low usage o/g on PAYG. BT may charge for their DV line but if you are going to consume minutes their 750 min package is competitive with VoIP providers. All the main players have fill your boots plans.
I think a lot more consideration is required before selecting a particular consumer voice technology.
Personally for seated outgoing calls I use a Yealink MP50 office phone which connects via Bluetooth to any 4G phone. The Yealink detects my iPhone 13 as soon as I am in the "office" which invariably uses WIFI Calling.