Cannot boot into Ubuntu installed on an external SSD after installing Windows with Boot Camp

I have a MacBook Pro running macOS Mojave and an external SSD with Ubuntu installed on it. The way I swapped between macOS and Ubuntu was by pressing the Option/Alt during boot to choose between Macintosh and EFI Boot (when the EFI Boot was selected it booted Ubuntu automatically).

Now I have installed Windows with Boot Camp and the EFI Boot has disappeared. Now I can only choose between Macintosh or Boot Camp.

How can I boot into Ubuntu with the external SSD again?

This is the output of running diskutil list:

/dev/disk0 (internal, physical):    #:                       TYPE NAME                    SIZE       IDENTIFIER    0:      GUID_partition_scheme                        *251.0 GB   disk0    1:                        EFI EFI                     209.7 MB   disk0s1    2:                 Apple_APFS Container disk1         180.0 GB   disk0s2    3:       Microsoft Basic Data BOOTCAMP                70.8 GB    disk0s3  /dev/disk1 (synthesized):    #:                       TYPE NAME                    SIZE       IDENTIFIER    0:      APFS Container Scheme -                      +180.0 GB   disk1                                  Physical Store disk0s2    1:                APFS Volume Macintosh HD            121.0 GB   disk1s1    2:                APFS Volume Preboot                 46.7 MB    disk1s2    3:                APFS Volume Recovery                509.7 MB   disk1s3    4:                APFS Volume VM                      1.1 GB     disk1s4  /dev/disk2 (external, physical):    #:                       TYPE NAME                    SIZE       IDENTIFIER    0:     FDisk_partition_scheme                        *240.1 GB   disk2    1:                 Linux_Swap                         8.0 GB     disk2s1    2:                      Linux                         40.0 GB    disk2s2    3:                      Linux                         192.1 GB   disk2s3