A Galaxy Tab S6 mounted flat on the wall as a Home Assistant control panel, held by a hidden slide-on plate and charged through its own contacts, with nothing plugged in and nothing showing. This site holds the parts list, the design drawings, and a page to hand to a 3D print shop.
This site: https://wallplate.daha.us/ · also reachable at https://www.brentrussell.com/wallplate/
Every part, one link each: the tablet, the printed parts, the pins and glue, the attic power supply, and the Zigbee coordinator, plugs, siren and sensors.
How the mount works: seven dimensioned drawings, cross-sections through the tongue and the pin block, the on-and-off sequence, the alignment procedure, and CAD renders of the three parts.
Just the three STL files, print settings and renders. Send this link to whoever is printing the parts.
A small plate screws to the wall with a raised tongue. A U-shaped frame glued to the back of the tablet drops over the tongue and hangs on it, hooked under its flanks so a knock can't pull the tablet off. Four spring contacts on a block at the plate's bottom edge press against the tablet's own charging pads, fed by a 12 V supply in the attic and a small converter behind the plate.