It turns out I can't run it on my phone: my model is too outdated. This is not a huge shock: I first got this phone three or four years ago, and the model was first released in June 2010. It'd be silly to upgrade just to play Pokemon Go, but it has struck me that my phone is no longer particularly good at doing the things I have always done on it. Twitter "upgraded" its native app to a version that runs so slowly on my phone that most of my Twitter usage from the phone now is "replying to direct messages". The app can handle this. It can't really cope with reading my feed any more. No client Twitter apps will run on my phone. Evernote runs but loads slowly. Google Docs is even worse. The browser is painful to use, too. I don't even like to read books on it any more. I did a factory reset a few months ago and only reinstalled the things I use all the time, but it didn't help. Everything is slow and crash-prone.
So I did a cursory web-search for my primary and inflexible requirement of a smartphone: a side-slide keyboard. One article dated June 2016 turned up ten "current" models, and I was briefly heartened.
Then shaterri pointed out that only one of those was more recent than 2013. The one that's from 2015? Has a physical keyboard, but it's a vertical slide, not sideways.
A less-cursory search did not turn anything more recent up.
I type at 45 wpm on my smartphone. I write books on my smartphone. I have tried using virtual keyboards and found them painfully, horrifically slow. Maybe if I practiced with Swype or something I could get up to a reasonable speed? Because 10-15 wpm is not a reasonable speed. That is a give-up-and-do-something-else speed.
But it's kind of horrifying to think that a signficant part of my work process is dependent on a style of device that's fallen so far out of favor it may never be manufactured again. I guess, in a year or two when my smartphone's performance goes from "bad" to "unusable", I will have to learn to get really really good with Swype or tote a laptop everywhere or something.
But I can't use a laptop while waiting in line at the store or taking a walk or using my exercise bike.