I finally found a FOSS Android keyboard with functional swipe / gesture typing. It's less forgiving than GBoard si you have to go slower, but I'm happy to be sending less data to Google. Even though it's in early development, the whole app is quite polished; more so than any of the other FOSS keyboard apps I've tried.
GitHub - florisboard/florisboard: An open-source keyboard for Android which respects your privacy. Currently in early-beta.
https://github.com/florisboard/florisboard
@MrGoat
That's very cool! I could see it being beneficial for people with RSIs or fine motor issues, depending how you set it up.
I do wonder if this might be infringing on a Leap Motion patent...