on 02-03-2023 16h21
BT Digital phone is a bespoke system that BT use. It will only work with the Smarthub 2 and will not work with any other router.
If you don't want to use it you can use any VoIP phone service that you want.
on 02-03-2023 16h22
See link about BT Digital Voice
Solved: Digital Voice FAQs - BT Community