Buzz is great software, the modular concept was fantastic. I don't think Oskari has worked on it since 2016 - http://jeskola.net/buzz/beta/files/changelog.txt
It still works though, and there is something of a community - http://forums.jeskola.net/
MilkyTracker is UI compatible with FastTracker 2, Schism Tracker is UI compatible with Impulse Tracker and Scream Tracker.
Renoise is more of a crossover of digital audio workstation with a tracker.
So far, Schism Tracker is more usable I've found, but it feels like running Impulse Tracker in DOSBox, which, granted, it not necessarily a bad thing.
In the end, I may just suck it up and pay for Renoise.
Renoise is the kitchen sink, its probably the most powerful tracker you can get, a bit overwhelming even to someone like me that spent over 10 years every day using them: https://www.renoise.com/
It's multi platform tracker with modular synthesizer functionality.
It only needs that sf2 compatibility to reach absolute perfection.