I had tried to explain this in my first post. I am sorry if I wasn't clear. Teensy 3.6 has the necessary hardware: the software could be a considerable amount of work. Perhaps hundreds of hours (for an experienced developer). However, the libraries exists and it is doable.
Perhaps their USB Host 3.0 software will handle MIDI, but at present they don't even show it as something they plan to do in the future if I read them correctly.
I think you must have misunderstood or chanced upon an old post. Paul S's USB Host library is at
https://github.com/PaulStoffregen/USBHost_t36 Check out midi.cpp therein for the T36 MIDI host implementation. Warning: it is officially "experimental" so to that extent you would indeed be "on your own", but not starting from scratch.
I'm still looking around for something that would do this job with some "lite" programming language like Arduino
Not so "lite". Perhaps you do not realise the Arduino "programming language" is C++? I use PlatformIO with MS Visual Studio Code for my K66 (Teensy 3.6) development. Worth checking (it is all free) if you're serious about developing on this.