Fully Kiosk Browser has a Javascript API and a REST API that allow you to remotely control the tablet hardware that the browser is running on. You can do things like play audio files, send TTS, turn the screen on/off, turn a screensaver on/off, set screen brightness, etc. It also has the ability to report back hardware information like battery levels. I think it would be nice to have this integrated into HADashboard with a custom component for HomeAssistant, so that you can set up automations that can control the device (like turning the screen off at bedtime).
fully is an android app that is run by someone else.
in the link you show there is step 1 to 5 to integrate the optional output from fully into HA.
then there is an step to use that output into the floorplan.
that approach itself isnt smart and not like HA, because the way its setup is to use the output from fully through HA specific for floorplan.
fully itself should be integrated into HA, so that it can be used without floorplan.
then it also can be used for dashboard.
a direct integration from fully into dashboard wouldnt be a wise approach.
off course its also possible to create an app that uses the mqtt output from fully and the mediaplayer outputfrom fully.