Anything is not a useful comment. When? I'm asking for a use case, I haven't seen anyone use them for a specific reason to use Linux. I'm asking about sensors and software that works together better than using it with an MCU
Another I have thought doing is ADS-B receiver mounted outside. It helps to put the receiver close to antenna so would put the SDR and Pi in enclosure, and power it from PoE. Microcontroller can't run the SDR. Micro PC is overkill and wouldn't work in enclosure. Doesn't use GPIO pins.
Linux would probably be very easy to built without needing firmware
I've also used GPIO on a Raspberry PI Zero W to build a Stratum 1 NTP server with nearly spooky accuracy with the PPS line.
Both things worked very well. They were compact, performant, used an inconsequential amount of power, and were very inexpensive.
And both things were very easy for me to implement, largely due to the tremendous amount of software available in the Linux-ey ecosystem.
If I were trying to bodge an MCU into performing these tasks without involving Linux, I'd probably have never gotten either of them done.