macOS Sierra Spotlight extensions
macos, macos-sierra, spotlight
Solution
Yes it is. Github user w0lfSchild is still actively maintaining this project: https://github.com/w0lfschild/Flashlight, which also allows writing your own plugins. It is actually a fork of the Flashlight project mentioned in the post you linked to
Problem
Unfortunately I could not find anything up-to-date online about this topic. Similar to the question stated here: OS X Yosemite Spotlight extensions, is it possible by now to extend Spotlight on macOS Sierra?