- Copied Debian Stretch netinst based on the instructions of Debian USB installation. Use the UEFI method.
- Copied the latest .deb firmware-iwlwifi with non-free iwlwifi drivers for Bullseye. I think the .deb can be copied into the root directory of the USB disk. I had extracted the .deb and copied the ucode files at the root of the USB disk. Debian might still complain that 2-3 ucode files are missing, but it should work anyway.
- Boot the laptop. No need to run the Windows installer.
- Enter the BIOS:
- When the Dell logo appears, press F12 many times (no need for the Fn key) to enter the boot menu
- .. or F2 to go direct to BIOS
- had to disable UEFI and SecureBoot so that the USB disk (with Debian Stretch) is detected.
- Change System Configuration -> SATA, use AHCI mode (not "RAID mode", whatever that is).
- Secure Boot -> Secure Boot Enable, and un-tick the box to disable.
- POST behavior -> Fastboot: Thorough (instead of Minimal/Auto).
During the installation, the Debian Installer complained about not being able to find the installation medium. I ended up coping the .iso file in the USB disk (which seems redundant). Then I went to a console (Alt+f3 or something) and did "mount /dev/sda /cdrom".
It detected my wifi access point, but would fail to exchange WPA keys. I tried a few times, eventually typing in my SSID manually, and that worked.
During disk partitioning, I chose the automatic mode with LVM and disk encryption. I had to go in the LVM config to remove the 16 GB swap partition.