My father is currently with 2degrees on a chorus fibre connection using a Fritzbox 7490 and landline (provisioned to one of the phone ports on the Fritzbox).
He's looking at switching to Spark and we'd prefer for him to keep using the Fritz rather than switch to the Spark Smart Modem. If we were to do that, as far as I remember from doing the same thing myself a few years ago, the internet will just continue to work without him having to reconfigure anything, but how about the landline? Will we need to connect it to the POTS port on the ONT rather than the phone port on the router? Can't quite remember but I'm sure 2deg and Spark do things differently in this regard.