Goodmorning,
On my system I have the following partitions setup:
-> a / EXT4 partition with openSUSE Linux 15.1;
-> another / EXT4 partition but entirely encrypted with Ubuntu 18.04.4;
-> a /boot partition with GRUB (originally created by Ubuntu).

Recently, I have noticed that after a kernel update, openSUSE updates GRUB removing other entries and leaving just the one about openSUSE itself, (it happens in both cases other entries are GNU/Linux distributions, Windows or BSDs). I have seen this happen in the last versions of Leap (if I correctly remember it didn't happened on openSUSE 13.1 or 13.2).

Since the Ubuntu partition in this case is encrypted, I think it is somewhat justified that he cannot find another OS, so I would like to know if someone has an idea about the best way to configure GRUB on the openSUSE side to handle correctly this situation.

The best solution, yet uncomfortable, I thought is to configure on the YaST side
-> Custom boot partition on the same /boot
-> every other check disabled (so it does not touch the boot loader)

and whenever openSUSE gets a new kernel I run update-grub / os-prober from Ubuntu.

What do you think about that? Does someone has a better solution for this problem?

Thanks,

Best Regards
hawake