Ardour

I like Ardour, but when choosing btw Ardour and Reaper - if you work with many VSTs or just exploring, this may be an interesting read: https://ardour.org/plugins-in-process.html

all plugins in Ardour run in the app's process, so if one crashed - you might lose the project.

But UX for MIDI editing in Ardour is so much nicer than Reaper's to my taste.