Created attachment 762755 [details]
Compressed YaST2 logs

My system has a GPT partitioning scheme and does not use EFI. I also put the
boot block at the start of the active partition, and have generic boot code in
the MBR. The active partition is indicated with the legacy_boot flag.

A partial df for the system is:

Filesystem                 1K-blocks      Used Available Use% Mounted on
/dev/sda3                   60213124   9954072  47170668  18% /
/dev/sda6                   53826316  32795236  20576144  62% /var/tmp
/dev/sda7                   51255784  20631016  28050216  43% /TW
/dev/sda4                   60344404  22760752  36522788  39% /Leap42.3
/dev/sda5                  711705020 393141448 282387980  59% /home
tmpfs                         809360        20    809340   1% /run/user/1000

Looking at the partitions with parted:
GNU Parted 3.2
Using /dev/sda
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) print
Model: ATA Samsung SSD 850 (scsi)
Disk /dev/sda: 1024GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: pmbr_boot

Number  Start   End     Size    File system     Name  Flags
 1      1049kB  9437kB  8389kB                        bios_grub
 2      9437kB  16.8GB  16.8GB  linux-swap(v1)        swap
 3      16.8GB  79.7GB  62.9GB  ext4
 4      79.7GB  143GB   62.9GB  ext4                  msftdata
 5      143GB   883GB   741GB   ext4                  msftdata
 6      883GB   939GB   56.1GB  ext4                  msftdata
 8      939GB   971GB   31.5GB  ext4
 7      971GB   1024GB  53.5GB  ext4                  legacy_boot, msftdata

(parted) quit

In this case, partition number 7 will be booted. Running YaST => System => Boot
Loader changes nothing. If I want the automatic boot to choose Leap 15.0, I
need to manually toggle the legacy_boot flag on partitions 7 and 3.

Attached is a compressed copy of the /var/log/YaST2/ directory.