The best de-Googled phone is, sadly, an iPhone. I came to this conclusion after sticking with Android for over a decade and hating iPhones, but switching to iOS has been one of the better decisions I made in my life.
If I could get a dumb phone that could still run Google/Apple/Any Maps for GPS purposes, I'd be first in line.
The smartphone UX is all kinds of poor, I'm immediately repulsed and turned off by it versus a keyboard and mouse. Hamburger menus at the top of a now-very-tall screen? Yeah, fuck that.
There's also the YouTube app (needed for Chromecasting YouTube from iPhone), and Google Calendar.
(I'm sure it's at least somewhat intentional along those lines that it hasn't become GTube or something over the years.)
I have just one Google app installed: Maps. Its location settings are set to only allow location access when the app is open, so it collects very little data useful to Google. I can probably switch to Apple Maps, but I don't know whether the quality of navigation and public transport data is as good as Google Maps. If it turns out to be similar, I'm likely to switch, because I'm only staying with GMaps thanks to the data quality.