By trying to install on a environment with systemd-boot the nvidia drivers through repo-non-free, even if it generates kernel loader blacklists as such:

grep -i 'blacklist nouveau' /etc/modprobe.d/*
/etc/modprobe.d/blacklist-nouveau.conf:blacklist nouveau
grep -i 'blacklist nouveau' /lib/modprobe.d/*
grep -i 'blacklist nouveau' /usr/lib/modprobe.d/*

it is unable to deactivate nouveau. The only hacky solution was through kernel parameters such as rd.driver.blacklist. After some debugging, it was clear that GRUB2 was in fact working just right, requiring just a simple restart after installation and the culprit was in fact systemd-boot.

Basically, systemd-boot isn't using directly dracut -f for initramfs regeneration, but sdbootutil mkinitrd. So after installation, I had to use sdbootutil mkinitrd manually in order to actually blacklist nouveau.

The package scripts should be able to distinguish between a GRUB2 and systemd-boot to use the required regeneration tools. Same applies to nvidia own run script tool. SDB:NVIDIA drivers wiki should indicate this case too.

Ref. https://forums.opensuse.org/t/unable-to-blacklist-nouveau-even-with-blacklist-nouveau-conf/176785/31