In preparation for a trip to Austria next year, I've bought a Smartphone (Pixel 3a XL) for the first time, along with Google Fi. In theory, the coverage shouldn't reach my house, but it usually does, although several conversations have ended up going across my WiFi (there's a symbol that tells me this.) Once I've been skiing enough of the mountain, I'll report back. I like that they only charge you, for real, for data used, not in blocks. I don't have my second bill yet, but an only expecting $1.30-ish as I've turned off mobile data and only used it experimentally. The phone also has the ability to add a SIM (I'm using the eSIM at the moment). I'll do that if coverage at the mountain sucks and I still need Verizon and if I can figure how to use the Smartphone conveniently while skiing. My flip phone is pretty bomb proof and the battery lasts forever, so it'll be hard to give up. In the short term I'll be using both.
In this neck of the words, Verizon rules, so I'm guessing that if I can manage the smartphone usage (battery life and worry about breaking it--the flip phone probably has been dropped hundreds of times in its lifetime and is no worse for wear, plus it fits in smaller pockets), I may be going the dual SIM route. I read that Android 10 can have them both operational at once, but haven't tried that yet. Even if I have to flip back and forth, that's fine.