When I installed Arch Linux with manually way without adding EFI partion and grub configuring, because EFI is already exist, It didn’t appeared in the GRUB2.
I solved it by updating bootloader by using Yast2 Bootloader by clicking OK in the GUI menu.
But when I installed CachyOS, this way just didn’t help…
CachyOS installed with UEFI general Udisk (partition 2) - name of USB flash drive from boot menu - on one GPT disk alongside openSUSE Slowroll on BTRFS partion with flag root and root mounting point, of course.
os-prober output from openSUSE:
➜ ~ sudo os-prober
2233.031281 | DM multipath kernel driver not loaded
/dev/sda1@/efi/Microsoft/Boot/bootmgfw.efi:Windows Boot Manager:Windows:efi
/dev/sdb3:CachyOS:CachyOS:linux:btrfs:UUID=4436983b-f4f5-4e0b-9378-2c815465d97a:subvol=@
➜ ~