I tried to reconstruct the issue using Virtual Machines. I took an Ubuntu 18.04.2 VM with Linux 4.15 and added a second disk. I booted that VM from the ISO with Xubuntu 18.04.2 and installed Xubuntu on that second disk and it rebooted after install without any problem. So I have to retry it on the real hardware.
However I rebooted Ubuntu from the first ext4 disk and that showed a part of the problem. The command 'update-grub' does not detect the btrfs system see my annex. The ext file manager shows the btrfs disk with the @ and @home folders a second window of the file manager shows the @ root (sub-)volume. However the terminal with the update-grub shows, that update-grub does not detect the btrfs system. I try it again on the real HW now, with its many many partitions and many disks. I use my gsm for the photos. ** Attachment added: "btrfs-from-ext4-os.png" https://bugs.launchpad.net/ubuntu/+source/ubiquity/+bug/1816240/+attachment/5239327/+files/btrfs-from-ext4-os.png -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1816240 Title: Impossible to boot 18.04.2 from btrfs To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubiquity/+bug/1816240/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs