I don't miss my N900; I still use it. I do not use it so much as a phone and more as a pocket computer. Install PostmarketOS on it with Emacs. Made a configuration that is very comfortable with the keyboard. I actually use daily, using it to write my journal, emails, have Telegram working on it within Emacs. Even whip it out in the train now and again to do some explorative coding. My favorite use of it is writing down my dreams at night. I can do this blind at night, don't have to look at the keyboard or screen which is excellent for dream recall.

For all these things the device is perfect. Though actually browsing the web with a modern browser is a no-go it is simply too slow. Would give a lot for a modern replacement. I have looked into the Gemini PDA though it is not the same as you need to put that device down on a surface to really use it. Not so with the Nokia N900. If anybody knows of a modern equivalent, please tell me.