N900 daily driver/main phone and Motorola Droid 4 XT894 with LineageOS 13 for whatsapp (bought a cheap pre-paid card)
Not sure what I will use a couple of years from now, still pretty pleased with my N900 and the Droid 4 is fine for what I need it for as well.

Hope to see an image developed for one of the two that will be future proof (e.g. native debian).

I also keep an eye on the qwerty device from Chen and the Neo900.