Installation stuck at "Random seed file" writing

I’m a total NixOS newbie, as I started to learn today. So maybe my question is obvious, but I’m stuck on it for about 2 hours.

The nixos-install command seems to run well until the installation of the boot loader (systemd-boot) where, I don’t understand why, it stops at the line :

Random seed file /boot/efi/loader/random-seed successfully written (512 bytes).

And then nothing, the shell seems stuck, nothing to say if it crashed or is just performing really long operation (It’s been an hour since my last try). I noticed no writing on disk since that (with $ watch df launched on an SSH login).

Many thanks for your help.

My (very early) NixOS config.

The laptop I’m trying to install NixOS on.
I heard about it having some UEFI limitations concerning Linux, perhaps it’s the source of the problem.

Ok so talking about how bad the UEFI implementation of this laptop is, I realized that I already had problems with it trying to use efibootmgr while installing Arch Linux.
So I disabled the (attempt of) modification of EFI variables with that line and it worked.

Hoping that will help someone.