I did a while back but pretty much lost interest for two reasons:

1) Difficulty wrapping my head around the programming which is basically C++. My mind just doesn't work in a manner consistent with logical programming.

2) Never found anything worth actually messing with beyond "Gee, that's cool, now what?" projects.

So, does anyone here have ideas for practical applications?

I looked into it a few years back.
I found that every time i came up with a potential project that I could have used this to create a solution to, i always found an off the shelf solution was already readily available so I have never tried using it.

I have 2 car related Arduinos cooking. One is officially a Speeduino and runs the fuel injection and ignition in my old VW Beetle.

https://speeduino.com/home/
Youtube video of Beetle idling. The distributor is only there to plug the hole.

The other is a body control module for same. This is in-progress but right now it controls the dome light and I intend to add automatic headlights

I see more ESP32 stuff now, and that opens a few things up. Practical things for shops include stuff like gate management in dust collection systems, etc.

Or, make lights come on in dioramas from your phone.