I wrote a blog post about exactly this in 2021 when the US was shutting down their 3G networks. https://benergize.com/2021/07/16/were-shutting-down-our-3g-n...

I had a OnePlus 3T and really didn't want to let it go (particularly because it DOES support VoLTE!) but ultimately got a Pixel 4 and have been using it since.