Thank you for Jake suggesting the Unihertz. Long ago, I had devices in a similar form factor. Sony Ericsson P990, Nokia E70, E71 and E6-00 comes to mind. While useful for brief notes and basic messaging, they wouldn't do for things like taking real time meeting notes or working with larger documents. The longest text I've written on my Cosmo so far, is a bit over 800 000 characters, and it's not done yet.
For such use cases, putting a Gemini, Cosmo or Astro on a table and typing with both hands, is about as small as I can go. Once upon a time I had a Psion Revo, with a keyboard layout similar to the Planet devices, but rather than 14.5mm, the letter keys were about 13mm wide, which was too small for me, so something like a fxtec pro1x would probably just end up being frustrating for me.
I have a reasonably good (non backlit, unfortunately) foldable Bluetooth keyboard, with an integrated phone holder, 15.5mm wide letter keys (and dedicated keys for Å and Ä). It looks like this (Gemini keyboard and a swipe card for scale)
While nowhere near as convenient as an integrated keyboard, it at least works with most regular smartphones.
Oh, well, this is sliding off topic. Planet still hasn't replied to my third email in about a month, so I guess it about time to go shopping. Would the Astro ever return, it might be good to have a fully working spare phone, unless I'd find a new home for it. We'll see.