How to Dual boot Arch Linux and Ubuntu Linux
Grub Customizer:
Grub Customizer is a useful UI tool for modifying the default Grub boot loader settings. By using this tool, you can add, remove, and re-arrange boot menu entries. You can edit kernel parameters and also choose to change the time delay at boot, in order to boot from the default entry.
OS-PROBER:
os-prober has been disabled by default, you need to uncomment/add
GRUB_DISABLE_OS_PROBER=false
to /etc/default/grub and run sudo grub-mkconfig -o /boot/grub/grub.cfg.