I never booted into more than one OS, I only have one. I’ve no use for the 5 seconds for selection.

I’ve no clue what bootloader I have… I think not grub, because I cannot find any grub files besides

/etc/grub.d/ with 2 files: 15_ostree 35_fwupd

and grub-mkconfig -o /boot/grub/grub.cfg results in bash: grub-mkconfig: command not found

I remember in the past turning off the 5 seconds, but I reinstalled my system after Plasma 6 release.

I use EndeavourOS with KDE if that matters/helps.