Currently using it with the built-in keyboard of the Unihertz Titan Pocket. Also used it with the regular Titan, the Fxtec Pro1 and the Blackberry Key2. All of these devices have proper hardware keyboards.

On the Vimium side most functionality works the same as on desktop. Tab switching using Vomnibar.activateTabSelection and Vimium's search are the exceptions. You can of course still switch tabs and search the normal Firefox way.