PC tries to boot removed OS

[BUTURUM]

After I have installed kubuntu on my PC, replacing openSuse and rebooted it I faced grub rescue screen. All partition was "unknown file system" and other ways of fixing problem through rescue screen didn't work.
I open BIOS boot menu and saw two options from the same build in SDD drive. As it appears my PC was still trying to boot openSUSE, which as I thought was replaced by Kubuntu (I didn't remember to choose dual boot).

Obviously I can manually open BIOS every time I turn my laptop on, but I won't. Are there some safe ways to remove openSUSE from boot options?

[JeffRedd]

Are there some safe ways to remove openSUSE from boot options?

I personally don’t know of any. I think that at this point, since the system is so new you should just re-install. This would be the best and most sure way to fix your problem. When reinstalling, make sure you do a complete format of the drives to make sure that everything is completely erased because you don’t want any leftovers. This normally doesn’t take long and it will assure you a clean system without the boot problems of another operating system that is only halfway installed.

[claydoh]

I personally don’t know of any. I think that at this point, since the system is so new you should just re-install.

Good lord no , that is not necessary. Reinstalling the same way will result in the same outcome.

After I have installed kubuntu on my PC, replacing openSuse and rebooted it I faced grub rescue screen. All partition was "unknown file system" and other ways of fixing problem through rescue screen didn't work.
I open BIOS boot menu and saw two options from the same build in SDD drive. As it appears my PC was still trying to boot openSUSE, which as I thought was replaced by Kubuntu (I didn't remember to choose dual boot).

Obviously I can manually open BIOS every time I turn my laptop on, but I won't. Are there some safe ways to remove openSUSE from boot options?

If you did not format your EFI partition during your Kubuntu install, or if that partition is on a different drive than your Linux install, the boot files from Opensuse are (likely) still present there.
Is your system using multiple drives? Is Windows installed?
What exact options are you seeing ion your BIOS?
Are you booting to Kubuntu from a different BIOS menu entry?

Often you can remove boot entries from your BIOS settings, but not always. You definitely should be able to change the boot order from there, and keep you from needing to use a hotkey at every boot.
You can also gather some information using the efibootmgr command, which can also be used to delete the Opensuse entry.

More details about your system and what you see will be helpful to determine a path.