I found out a fix / workaround, so I don't know if this still is a bug or not. grub2 will actually install with a BTRFS /boot if the disk partition table is converted from MSDOS to GPT, AND a 8 MB bios_grub type EF02 partition is created.
Then grub2 will install.
I've noticed that, when booting from a BTRFS /boot, grub2 will shortly display a message stating « Sparse file not allowed », but then the system goes on booting without any other noticeable problem. (my /boot being "compress=zlib" mounted).
I found out a fix / workaround, so I don't know if this still is a bug or not. grub2 will actually install with a BTRFS /boot if the disk partition table is converted from MSDOS to GPT, AND a 8 MB bios_grub type EF02 partition is created.
Then grub2 will install.
I've noticed that, when booting from a BTRFS /boot, grub2 will shortly display a message stating « Sparse file not allowed », but then the system goes on booting without any other noticeable problem. (my /boot being "compress=zlib" mounted).