HeliBoard is a privacy-conscious open-source keyboard, based on AOSP / OpenBoard.
Does not use internet permission, and thus is 100% offline.

Features:
<ul>
  <li>Add dictionaries for suggestions and spell check</li>
  <ul>
    <li>build your own, or get them  <a href="https://codeberg.org/Helium314/aosp-dictionaries#dictionaries">here</a>, or in the <a href="https://codeberg.org/Helium314/aosp-dictionaries#experimental-dictionaries">experimental</a> section (quality may vary)</li>
    <li>additional dictionaries for emojis or scientific symbols can be used to provide suggestions (similar to "emoji search")</li>
    <li>note that for Korean layouts, suggestions only work using [this dictionary](https://github.com/openboard-team/openboard/commit/83fca9533c03b9fecc009fc632577226bbd6301f), the tools in the dictionary repository are not able to create working dictionaries</li>
  </ul>
  <li>Customize keyboard themes (style, colors and background image)</li>
  <ul>
    <li>can follow the system's day/night setting on Android 10+ (and on some versions of Android 9)</li>
    <li>can follow dynamic colors for Android 12+</li>
  </ul>
  <li>Customize keyboard <a href="https://github.com/Helium314/HeliBoard/blob/main/layouts.md">layouts</a> (only available when disabling <i>use system languages</i>)</li>
  <li>Multilingual typing</li>
  <li>Glide typing (<i>only with closed source library</i> ☹️)</li>
  <ul>
    <li>library not included in the app, as there is no compatible open source library available</li>
    <li>can be extracted from GApps packages ("<i>swypelibs</i>"), or downloaded <a href="https://github.com/erkserkserks/openboard/tree/46fdf2b550035ca69299ce312fa158e7ade36967/app/src/main/jniLibs">here</a></li>
  </ul>
  <li>Clipboard history</li>
  <li>One-handed mode</li>
  <li>Split keyboard (only available if the screen is large enough)</li>
  <li>Number pad</li>
  <li>Backup and restore your learned word / history data</li>
</ul>