Hello,
this screenshots give you an overview of my actual OH3 UI so far. Additionally I have a lot of motion sensors and automations so normally this UI is very rarely used (as it should be in a “Smart Home”). Everything is semantically modeled if useful.
The first screenshot shows the Overview page. Remarkable:
- “Beleuchtung” is lit up if any of the lights in the apartment is ON (lots of Hue Lightstrips, Bulbs, Filament, etc.). So you can check if any light is turned on with a glance
- “Verschattung” gets you to a shutter overview page, grouped by rooms as we have more than one shitter per room quite often
- There is a weather widget I got from this forum
- Presence is detected by using the iphone presence functionality and an iphone automation to switch an Openhab button visible in HomeKit ON and OFF
- “Radio” starts a special station on a Echo (using an Alexa Routine), in case of the living room it turns on the Ambeo soundbar (via Logitech Harmony) also and starts the radio station playing synchronously on the living room echo and the FireTV connected to the Ambeo soundbar and sets decend sound volumes

This screenshot shows the light overview page grouped by room. Remarkable:
- You can see there is light in the living room, the office and on the balcony

If you click on a room you see all the lights of a room. Remarkable:
- You see a list view of a light group created for this room, not an extra page
- For the filament bulbs I created a custom widget, I do not use the default slider

Here you can see some of the lights controlled by OH in the living room (by the way, every light in the apartment can be controlled by OH)

And in the office:

This is the shutter page grouped by rooms with the details for the living room. Remarkable:
- You see a list view of a shutter group created for this room, not an extra page
- I created custom widgets for standard shutters. So you can use buttons or a slider for each shutter in one widget
- For shutters with slats I created a custom widget with extra buttons to move the slats in an transparent position or closed position

This is the logitech harmony widget I found in this forum, called from the overview page:
A list view of all volume sliders of all my Echos and the Ambeo Soundbar, called from the overview page:
All controls for my Ambeo soundbar, controlled by the Harmony remote:
Temperature overview for all rooms (Guestroom does not want to switch to Celsius and continues to show Fahrenheit, I tried all I can, hrgrmpf)
Controls for my Xiamoi S6 vacuum robot, called from the overview page:
All the other pages are created totally automagically by using the semantic classification of the items.
Here are some examples:
-
The Location overview page:

-
The living room properties:

-
The bathroom equipment:

-
The equipment overview page:

-
All my wallplugs (except plugs connected to lamps, they are tagged as lights).
Wallplugs that must not be switched are readonly (they measure the used power, to notify via rule if the washing/diswasher is finished)

-
The vacuum called from the equipment page.
Notice the grouped items

-
And the direct control of the vacuum

-
All of the window contacts:

-
The properties overview page

-
All humidity sensors in the apartment:

-
And the graph for a day

-
All CO2 sensors

-
And the graph for 2 days.
You can see when I slept or worked in the office

Hope you get some inspirations for your own OH3 UI.
All this was created using all the help and inspirations from the folks of this forum. Keep up the good work 
Kind regards