when I worked in the embedded software industry long ago, I spent lots and lots of time connecting over serial ports to dev boards, using software like Minicom. Being able to do that in screen itself would be neat. Tmux does it.

Screen does connect to serial ports. Just open the device and append the line parameters you want to run on the port. Unlike modem dialers like Minicom, you don't have to screw around with on-hook off-hook distinctions or an intrusive TUI.

Ha, I have only ever used screen for serial comms and only learned about Minicom from this thread

Exactly the other way around for me! I've been using screen since forever, and had no idea it could do that. Minicom I still know from the dialup dark ages.

When I worked with embedded systems, I used both, and didn't really understand the differences and nuances between them, and now I wish I did.

Connecting to serial devices. You can for example get a USB uart dongle, and then connect cables to some device where you have uart pins. Most recently I was doing something like that for an esp32 board, and used screen.