FlorisBoard is in f-droid, and has swipe. What it doesn't currently have, and has been in the "to do" list for - I don't know, over a year - is autocorrect. This makes swipe far less effective than on other boards. But it does work well; there are just a lot of spelling errors to fix.
If it's feature complete, a keyboard doesn't need regular updates. According to the other thread it's not feature complete, so it could be abandoned. Since it's FOSS any enthusiastic person could stop it from being abandoned.
In using ASK with swore, but as you can see, it's not yelling accurate. I wish that the namespace key would remove the while worked, not letter by letter.
(I'm using ASK with swipe, but as you can see, it's not terribly accurate. I wish that the backspace key would remove the whole word, not letter by letter.)
You can set gestures on spacebar to delete whole word. This is why I say anysoft need a lot of time, because probably your needs are already fulfilled, but find the option is an ordeal
I'd suggest you openboard,
this version is a fork of the original one & is being maintained currently . Have a look at the readme and you'll find how to add gesture swipe.
Wait, is using GBoard with blocked internet access actually private? I read other people say it is like a keylogger, and probably would bypass the internet restriction.