Some weeks ago I posted a tutorial How to build an openHAB 4 appliance (openHABian with touchpanel) on a Raspberry Pi 4 which might be of interest for you. To reduce the load on a RPi with openhabian + a GUI I choose openbox with just a browser available. The tutorial leads to a touchpanel with habpanel as GUI. But you can use it with keyboard/mouse, too. And instead of automatically starting a browser with just habpanel available, you can just show the openbox menu to start the browser only when needed and allow full web access in it.
