Running Odoo v9 nightly on Debian 8.3 testing ("stretch") with POSbox addon (box-less) in chromium with a touch screen, I cannot get the on-screen keyboard to work.

I saw it once coming up but not reliably. Anything to watch out for, configure, install?

For now I am using the quite nice florence virtual keyboard, but that's cumbersome to use in the POS, since I want to run that one full screen and this hides the task bar icon of florence, obviously.

I checked https://www.odoo.com/de_DE/forum/hilfe-1/question/what-kind-of-hardware-is-supported-by-the-point-of-sale-49 and of course the keyboard option is activated in the POS settings.