I use Thumb Key. https://github.com/dessalines/thumb-key
It’s a privacy-conscious keyboard for your thumbs written by one of the creators of lemmy. It uses a 3x3 grid similar to the old t9. The idea is that you can touch-type much easier with only 9 buttons so you don’t need to autocorrect.
The web-based installer for GrapheneOS is very easy to use. The catch is that it only works for Pixel phones (and only those that are still receiving updates).
With Miryoku! https://github.com/manna-harbour/miryoku