What open source keyboard alternative you suggest instead of gBoard on Android?

Thumb-Key is aiming to be a FOSS replacement to the now unmaintained MessageEase. Like MessageEase, it offers a 3x3 touch-and-swipe layout. It takes time to learn, but allows to type fast and accurately, thus getting rid of the dependence on prediction/auto-correction, without which QWERTY on small touchscreens would be unusable. Many people report typing more than 50 WPM on MessageEase and the same should be possible with Thumb-Key. It's a young project and is still missing many features and gestures of MessageEase, but it is active and has a community here at thumbkey@lemmy.ml.

I only recently switched from GBoard to MessageEase and ThumbKey, and I still around 25 WPM, but I found that I stopped making mistakes when typing out the long master password for my password manage on my phone, because this is one of the areas where auto-correct couldn't help.

But I am still far away from reaching the speeds of swiping on a QWERTY-keyboard without word prediction. So if you don't mind that and don't want to spend your free time learning alternative layouts, stick to QWERTY layouts, but if you want a keyboard layout to type exactly what you want, try one of these 3x3 boards. To be honest, if you want to give it a shot, out of the two I would probably still recommend MessageEase, as Thumb-Key is very alpha, but that might change. I have both with the same layout and switch back and forth.