I do not see anything about Bluetooth MIDI in the linked page. That is just for establishing a Bluetooth connection. In my experience, Bluetooth MIDI requires more than just the Bluetooth connection. I do not think the Raspberry Pi or Linux typically listens or broadcasts BT MIDI. I can offer a couple other options that have worked well for me:
McLaren Labs RTP (Wifi) Midi ($5)
This application let’s you connect to other RTP devices (e.g. your Mac, or your iOS devices) over WIFI. You may need another iOS app on your iPad to establish the connection, like Midi Network, but you could also establish the connection from the Pi RTPMidi utility. This is ‘Network Midi’ from the iOS perspective. I’ve had great success with this RTP Midi. There is a free RaveloxMIDI option out there, but it was fiddly for me - once I switched to McLaren’s option I have never had to tinker with it to make it work.
CME Widi Bud Pro ($69)
I have used CME’s (Bluetooth 5) Widi Master and the previous (USB) Widi Bud successfully. If you get a single USB ‘Widi Bud’ for the Pi, you will be able to see it from your iOS devices that use Bluetooth Midi. It will not auto connect (that’s where multiple Widi devices shine, in addition to supporting grouping of Widi devices together).
Recompile BlueZ - ($0)
On the McLaren Labs site there is a post about setting up a Pi 4 for bluetooth Midi:
I have not tried this, but with some patience (and backup Pi images), it might provide a solution.
That said, I’m glad you posted - I had never actually tried connecting to my Pi via Bluetooth MIDI. If there is a (free) way to set it up, I look forward to learning about it in this thread.