"Argos is a GNOME Shell extension that turns executables' standard output into panel dropdown menus. It is inspired by, and fully compatible with, the BitBar app for macOS. Argos supports many BitBar plugins without modifications, giving you access to a large library of well-tested scripts in addition to being able to write your own."

https://github.com/p-e-w/argos

There is also a #KDE Plasma port, but I haven't tried it.