Remove GRUB from macOS Catalina So I installed Ubuntu on an external disk via my MacBook Pro 2016 with a USB flash. Now whenever I try installing another Linux distro such as Pop_OS I see the GRUB loader complaining about a bunch of stuff and I also had to change my booting disk to my macOS Catalina so I understand that GRUB is the main loader rather than the default macOS one. Is there a way for me to completely remove GRUB without having to reinstall macOS?
With Ubuntu, GRUB files are stored in the EFI/BOOT and EFI/ubuntu folders in the hidden EFI partition. Apply the following steps to remove the GRUB files.

Enter the following command to determine the identifier for the hidden EFI partition on the external drive.
diskutil list

For this example, I will assume the identifier is disk2s1. In the following steps, make the appropriate substitutions.

To mount the volume stored in the EFI partition, enter the following command.
sudo diskutil mount disk2s1

Note the volume name given in the output of this command. For this example, I will assume the volume name is EFI. In the following steps, make the appropriate substitutions.

Use the Finder application to view the folders in the EFI folder of the EFI volume (device). See image below.


Move the folders BOOT and ubuntu to the trash.

Empty the trash.

Enter the following command to unmount the EFI volume (device).
diskutil unmount disk2s1