I wanted to try this for just two weeks — my Pixel phone's battery swelled up, and the new iPhone wasn't coming out for a couple of weeks; I told my wife I'd be fine without a phone and she quickly vetoed it.

I did my usual investigation of flip phones and dumb phones; couldn't find one that ran Android or basic apps like Spotify and podcasts that I use every day *and* worked on major US cell carriers. There's some cool E-Ink phones out of China, but AFAIK they don't have full compatibility on US cell networks.

I ended up with an iPhone and I just dumb it down. Black background, installed only like a dozen apps, removed a bunch of the preinstalled ones, aggressively culled notifications.

Actually I've been thinking of removing the web browser from my iPhone. Your post inspired me to do it. Settings --> Screen Time --> Content & Privacy --> Allowed Apps, disable Safari. Let's see how I manage!