Kinetica

Kinetica is a keyboard for two thumbs at once. Each thumb swipes or taps on its
own, at the same time as the other, and the two streams merge into one word.

Typing "something": the left thumb taps S, then E, while the right thumb swipes
O -> M and then T -> H -> I -> N -> G. Kinetica merges them into S + OM + E +
THING.

It is a spiritual successor to the discontinued Nintype, written from scratch on
Android's public IME APIs: not a fork, and no third-party gesture or prediction
library. The dynamic time warping, the trie search and the two-thumb merge are
all in the app.

The app declares no INTERNET permission, so nothing you type can leave the
phone. Decoding, prediction and learning run on the device, and password or
private fields turn off suggestions, trails and learning.

Features

* Two thumbs, each read with its own cursor, so a word can pass between them in
any order; one tap can stand for a double letter
* English, Italian, Spanish, Polish, Czech, Dutch, German, French and Norwegian,
plus Russian, Ukrainian, Hebrew and Arabic as experimental: 46k to 50k words
per language with real corpus frequencies. Accented words are drawn on their
base keys and restored on commit
* Several languages at once: mix two in the suggestions, or let the keyboard
follow the language you are typing
* Next-word suggestions, recent words on the bar, and a correction strip right
after each word
* Tap inside a word you wrote to swap it for another; swipe shift to change
its case
* Tap autocorrect with three levels; backspace right after it undoes it
* Your words rank higher as you use them; slide a suggestion to raise, lower or
block it. Names you write with a capital keep it
* Chords on ?123 or the spacebar, edge swipes on any key, and text expansions:
type text, run an action, or press Ctrl and a key
* Long-press menus as grids, with your own list for every letter
* Keys that fit the field: @ in email fields, / in web addresses, and an
optional number pad for numbers
* Optional numbers row, a wider middle row, landscape split, one-handed for
either hand, split mode, adjustable height and margins
* Peck-type mode for slang and code: every tap types exactly its letter
* Dark, light, Material You or your own colour
* Backup of every setting, learned word and shortcut in one file
* Settings in English and Italian, with short tips and a two-thumb tutor

Source, build instructions and the full feature list:
https://github.com/EZ-eta/kinetica

If Kinetica is useful to you: https://ko-fi.com/ez_eta