Jeremy Bicha created an issue:
Caribou is the on screen keyboard used by GNOME Shell until GNOME 3.28.
While it can be used in an environment like GNOME Flashback, I don't think it's particularly popular there. I've heard good things about Onboard (except that it's difficult for it to be compatible with GNOME Shell on Wayland because that would probably need deep support in GNOME Shell.)
I believe Caribou is unmaintained and not used as much any more. Please consider moving it to Archive.