Update: 2024-09-15 - The easiest way to connect external MIDI devices to the Linux subsystem of your Chromebook is to use the free McLaren MIDI Server sending to McLaren Labs' rtpmidi for Chromebook Linux! (Debian 12 Bookworm).

Update: 2024-05-31 - McLaren Labs' rtpmidi is now available for Chromebook Linux! (Debian 12 Bookworm)
Read how: Install McLaren Labs' rtpmidi on Chromebook.Go to: https://mclarenlabs.com/store to get it!