It was the first time I
installed something in EFI mode, as in the past I always switched back
to legacy mode. So I'm quite sure I booted in EFI mode.
the installation and seeing that the computer was not booting, I started
to research in the internet and found the Debian installation guide I
mention in the bug report. After
that I started to understand what was going wrong and I installed again
Debian from scratch and without changing anything in the BIOS. But this
time I allowed partman to do a guided partitioning, which I afterwards
tuned to my needs. Partman of course included the EFI boot partition,
and this time everything went fine.