there is a fork with proprietary dependencies removed called Signal-FOSS, whose repo you can add to F-Droid if you decide to trust it
it's on F-Droid https://f-droid.org/packages/org.dslul.openboard.inputmethod.latin/
there is a fork with proprietary dependencies removed called Signal-FOSS, whose repo you can add to F-Droid if you decide to trust it