I'm interesting in developing a custom command-line class in Joomla4, but I don't know where to get started.
Can anyone provide a general example on how to set up a class for this purpose?
These are two references I think cover the basics and should get you started.
https://www.dionysopoulos.me/book/com-cli.html
https://magazine.joomla.org/all-issues/june-2022/joomla-4-a-powerful-cli-application
The second one is a little less focused on the development aspects, being a broader overview, but it does have a reference at the bottom with links to more reading.