For me personally, Jolla C2 is not ready as a daily driver. I will still use my Xperia 10 III until the moment, when 4G Internet and Voice calls are working in the 4G Network. Until than i will have a Linux Toy without SIM-Cards, where i can without any stress transfer all my data, install all the apps i need, set anything up etc. And in 1-2 month switch the SIM-Cards, when its ready. Nothing simple as this 
A little bit i don’t understand the people who buy a Jolla Community device with a beta state os and then complain, that its not ready for the daily usage.
What for estimate time you are asking for? Nobody would give you any estimate time. Because when Jolla say, its estimated in 2 Month, you will in 3 month say: “You promised me in 2 month 4G is ready”.
Its ready, when its ready, just keep calm. You have no other daily driver, which works with 4G?