This week, for the first time in more than a decade, the Blackberry is off and its SIM card removed. The card is in my Gemini. That was made possible by my flashing the Gemini with Sailfish OS, the configuration of which was made possible by the sage advice of Vader and Meganerd.
I made the switch when it became clear that despite a reflash the Blackberry was not going to be able to receive ProtonMail. Worse, the reflash to the latest (and, alas, last) version of BB10 also took away WiFi calling, which I find useful in that out here in the woods there is no cellular coverage. I don't have WiFi cellular with Gemini/Sailfish 2.14.14, either, but I do have ProtonMail and ProtonVPN, neither of which worked with the Blackberry.
As I understand it, WiFi calling is added to the next Sailfish OS release -- but the ability to receive ProtonMail is gone. Having poked around the sailfish community, I am confident that this will be fixed before long, I hope through a dedicated application. I've opted not to try an upgrade yet, because I have ProtonMail, ProtonVPN, and of course telephony out in the world, and I have a landline at home.
In a smartphone, I need telephone, email, and for the children, texting. The ability to browse or follow a link is good, but I've never found it to be of especially great utility. And anything else is gravy.
So yes, as of this week I'm using Gemini as my sole portable phone. And I'm -- so far -- pleased with it, and expect to be more so as time goes on and things get more sorted.