I grabbed it from FDroid to give it a try. I really don’t believe there could be any way to use this where the speed could even come close to a swipe based keyboard. Every character requires a full up down motion with your thumb and often an additional gesture to reach a sub letter and the subsequent space between words. With swipe style I can bang out entire words with their space in a single motion with about 85% accuracy. Thumb keys layout doesn’t map to existing keyboard layouts rather it prioritizes common letters with less common letters on gestures which failed me a couple of times because my direction was a little too up vs up right. Swipe typing has a huge leeway for errors including skipping letters while offering suggestions because it can see the entire word you attempted.

They could possibly add swipe functionality to this to improve the speed but given the center space contains 9 characters I’m not sure that would be possible to infer that much.

Maybe someone could really spend the time rewiring their brain to use this but I don’t think in it’s current state it can compete in WPM with a swipe style keyboard so it really comes down to how important the privacy features are to you.