Before you have a Linux terminal - boot menus

SUSE Linux Enterprise Server 15 SP5 LPAR mode z/VM guest KVM guest

Do not confuse boot menus with a Linux® terminal.

Depending on your setup, a zipl boot menu, a GRUB 2 boot menu, or both might be displayed when you perform an IPL.
zipl boot menu
The zipl boot menu is part of the boot loader for the auxiliary kernel that provides GRUB 2 and is displayed before a Linux terminal is set up.
GRUB 2 boot menu
GRUB 2 might display a menu for selecting the target kernel to be booted. For more information about GRUB 2, see SUSE Linux Enterprise Server 15 SP5 Administration Guide.