As a professional music composer myself and working on Linux with Ardour, I’d say it is overall pretty good since many years. If you don’t like midi in Ardour you can use another soft to runs midi notes. On Linux the good thing is that if you don’t like something you can change, specially with audio softwares.
To me the two major issues with professional music on Linux are :
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Proprietary plugins for virtual instruments are a nightmare (hard to make them to work, expensive on machine’s resources and unreliable),
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Most company still think free software = unprofessional/amateur, which can make it harder to get jobs.
Name, address, GPS localisation data, habits (like apps you often use, moments you use one device or another), gender, search terms in search engines, open web pages on a web browser, connection (other person you know), the work you do and where you work.
All kinds of things, really.
The usage is mostly advertising or identity theft.