I finally got around to installing ThumbKey, an alternative keyboard input method for Android.
I was braced for a mediocre clone of #MessageEase.
It is better than MessageEase.
I particularly like that with the "writer" layouts I can enter em-dashes and ellipses as a matter of course, and that the "compose" layouts allow easy input of accented characters. The return-swipe to get a one-off capital, overriding auto-caps, also helps with FediVerse CamelCase.
Goodbye, GBoard!