I tried a KaiOS based phone also in that time, but that was so unbelievably unstable that I ditched it after using it for two weeks or so.
I still have a smartphone powered off in a drawer, that I pick whenever I need that (~once a month, for banking stuff, using Google Maps to drive to another city, etc). I have Telegram running on my laptop and a few other things like the app for my mowing robot.
In general, also at work, I like to mute all notifications if I need to focus, heavy Pomodoro user, too.
There are not that many downsides for me. Sometimes someone asks me to send a phone number to them, which is only possible via Bluetooth. So I need to write the number down on a piece of paper, type it back into an SMS and send it. What a waste of time - I first thought. But in reality, that dump phone saves much more time, than these little pieces of manual effort cause, so in the end, I still have more free time. I was surprised at how often I do things that I don't need to do that often, e.g. checking my bank account balance.