The grub menu displayed as if the system knew which partition contains the bootloader. The root partition mounted by itself. Neither dmesg nor my init/process manager threw any errors. The boot partition was not mounted, neither was swap.
I did manually create an fstab from within the installed system and all is fine, so my question is purely academic. Do modern systems not need an fstab in order to know which devices and partitions to mount where?
If the initramfs is using systemd, it’s actually able to look up the root (by label) and ESP partitions (by guid) automatically. GRUB can also detect the ESP and enumerate UKI images. There’s still some assumptions being made, but it’s cleaner than ever.
Cool! In my case, it must be GRUB, then, since I’m not on systemd. Thanks!