For anyone still fighting with this, I just fixed it by forcing a few drivers to be available during boot, please don’t @ me if your pc explodes:
arch-chroot into your system, create a /etc/dracut.conf.d/usb-boot.conf with the drivers you need, in my case:
force_drivers+=" uas usb_storage xhci_hcd xhci_pci "
Then rebuild and check if the modules are actually listed:
sudo dracut-rebuild
lsinitrd /efi/*/*/initrd | grep -E "uas|usb_storage|xhci"
Reboot