www.makemkv.com

Sorry, I misunderstood.
It worked, this is what I did:

1/ Flash a first time with the MK firmware (https://forum.makemkv.com/forum/viewtopic.php?f=19&t=19113) in full (I suppose to get rid of encryption and flash the boot also) :

# sdftool -d /dev/sr0 rawflash full,enc,slim -i /home/richard/tmp ...

Thanks. How do you see it's not enabled? Is that a particular value in the sdftool --info output?

Tried this (with sdftool):

root@coyote:~# sdftool -d /dev/sr0 rawflash main,enc,slim -i /home/richard/tmp/mk-firmware-pack-20200720/MK/HL-DT-ST/BP55EB40-NB50/HL-DT-ST-BD-RE_BP55EB40-NB50-1.03-NM00800-212005070924.bin

Reading input file /home/richard/tmp/mk-firmware-pack-20200720/MK/HL-DT-ST ...

Hi, all.
I'm using makemkvcon on linux to flash my drive and it apparently works well. However, the drive reported by makemkvcon keeps the same name and I can't read UHD drives.
Here is the output of makemkvcon for the drive:

root@coyote:~# makemkvcon f -l
Found 1 drives(s)
00: dev_21:4, /dev/sr0 ...

Yep. That worked.
Thanks a lot.
I guess it's time to purchase a licence then.

Thanks for the answer.
Is there any way to add the key without the GUI, with makemkvcon?

Since my 1.8.9 installation had expired, I downloaded the 1.8.10 version as advised, compiled it then installed it.
Unfortunately, it still says the my setting is expired.
Since this tool is the only way for me to watch Blu-ray on Linux, I decided that nevermind, it was worth the purchase.
Going on ...