I too have btrfs formatted microsd card on my Jolla and it is "shared" with aliendalvik user space.

Or used to be as it is nether working for me.

But I got unlucky after pre-Update 11 and device is rebooting frequently whenever the shared microSD is in place.

Even if I systemctl disabled the mounting script.

Same occurred with after Update 10 and I had to factory reset phone and format the microSD card.

I can't wait for Jolla tablet arrival so I can dumb phone media to it.

But the new fixes and improvements in this update are great and my phone is stable enough without microsd.

Nevermore btrfs mircoSD and extra tinkering.