Comment by efreak

Keep your password manager offline with Keepass2 USB keyboard plugin for Keepass2Android [1], but I'm not sure how well it works. Too-fast USB keyboard input does seem to have issues (the open issue seems similar to things I've seen an AlphaSmart 2000/3000 do in USB emulation mode; PS/2 always worked fine).

There's also this other project, which seems more generic/difficult [2]

1: https://github.com/whs/K2AUSBKeyboard 2: https://github.com/pelya/android-keyboard-gadget