One of the side projects I work on is a scoreboard that displays MLB scores. It's highly configurable -- you buy the size panel you want and a Raspberry Pi, install the software, and you can configure it to display games, standings, and news headlines for your favorite team or division.
The problem is that the hardware is purchased by the end user, so it can come in many different sizes. I think we officially support 6 or 7 sizes right now, and each panel can be a chunk of change if you get a nice one. If we wanted to test on every device that means I need to shell out 50 bucks x 7 sizes, plus Raspberry Pi and wiring adapter, so not insignificant for a hobby project. Instead, I wrote a drop-in replacement emulator that makes it super simple to emulate any size panel across a variety of display types.
The most advanced display adapter spins up a minimal webserver and serves emulated images over a websocket, meaning you can display your panel over the network on pretty much any device with a web browser.
I write about it quite a bit, if further interested: https://blog.ty-porter.dev/categories.html#emulation-ref