Planet Computers' laptop-like Cosmo Communicator phone just became that much more useful to its audience of very particular power users. The Cosmo now supports a promised multi-boot function, letting you run Android (both regular and rooted), Debian Linux and TWRP on the same device without one replacing the other. You'll have to partition your storage and know your way around a boot menu, but this will give you a way to run Linux apps or otherwise experiment with your phone.
You won't lose over-the-air updates for Android by installing Linux, Planet Computers said.
The multi-boot firmware is available for free, and there are instructions for installing Debian and other software. This still isn't for the faint-hearted. However, it also represents one of the few instances where a phone maker has officially enabled support for operating systems besides the one that ships with the device. The Cosmo is also fairly well-suited to Linux thanks to its keyboard -- you won't have to jump through hoops to use the command line.