This issue seems intermittent.  Sometimes it works fine then it stops.  Sometimes exiting and launching again fixes it, sometimes it doesn't. It happened once in 1.16.0.67 but fixed itself after relaunching and didn't happen again. In 1.16.0.68, I haven't been able to get it to work again as yet with several re-launches. It's very odd as the keyboard works fine for everything else including the in-game chat window and any other text input boxes but it doesn't work for jump/fly/swim and if I go to the keyboard settings, it doesn't let me set anything to use the spacebar.

It happens with both of the physical bluetooth keyboards I own: an ARTECK HB030B and an Anker A7726J11. My device is a 2019 Samsung Galaxy Tab A SM-P205 running Samsung's stock Android 9 with the latest updates from Samsung.

I never experienced anything quite like it in 1.14. The closest thing to it is how mouse button support has always been broken on Android.
 
Update: Alt-Spacebar seems to work when Spacebar alone doesn't. Shift-Spacebar and Ctrl-Spacebar don't. It's as if jump inexplicably requires the Alt modifier.