refind does not search for Operating system on external GPT device

Hello
I have an external drive that I formatted with a GPT partition table.
unfortunately the bios of my computer is badly done because it does not offer to boot with the files of its FAT32 partition.

I have been using refind installed on the internal disk for several years.
He no longer knows how to explore this external drive despite numerous refreshments.

I just installed ubuntu 20.04 in a partition on this external drive. Ubuntu is not automatically detected.
As a palliative, I used a trick. I made an additional boot partition which I installed in the internal disk

I know that I could also make a manual entry defining the characteristics of this Ubuntu because I have already done for other cases.

I do not understand why automatic detection does not work on external gpt device
I looked at all the settings but I found nothing in particular

precision
When the computer boots, if the external drive is connected, it is called /dev/sda and the internal drive is called /dev/sdb
If the external drive is plugged in later, it is called /dev/sdb. In this context, it is normal to do a new research

However in both contexts, nothing is found in this disc

Thanks for giving me an idea.

Good week