Hi Jon - you can! There’s a lot of useful stuff out in the wild, too, but I would be careful about what you install on a production instance until you know it works as expected; some repositories are more actively developed with fewer bugs than others.
Frappe is actually starting to move some things into separate modules (like Healthcare), and shipping has been standalone from the get-go. How to do it is explained here. So, for example, if you wanted to install the shipping app, you would use these bench commands:
bench get-app GitHub - frappe/erpnext-shipping: A Shipping Integration for ERPNext
bench install-app erpnext-shipping
I think there’s a way to do it from Frappe Cloud for those who have a hosted instance there (and Frappe actually lets you install a handful of apps that are preloaded as options in the UI), but I’m not sure how that works.