I used a feature phone for several years, and held on to it for as long as possible. It was based on KaiOS (formerly FirefoxOS) and in fact, a neighbor of mine

I used a feature phone for several years, and held on to it for as long as possible. It was based on KaiOS (formerly FirefoxOS) and in fact, a neighbor of mine had a very similar phone that included an app store. Mine didn't, but still integrated with Google properties such as Mail and Calendar. Not very well. It did include a web browser, and I could visit web pages using mobile data or WiFi. The browser was very limited but usable, with some zooming and panning available. I appreciated the constraints and security of that sort of phone, but once I upgraded to a smartphone I was immediately addicted.