You can ignore that - the warning has appeared for years with no ill effects:
I’ve had the same warning every time I’ve updated or installed a kernel on my mini-PC ever since I installed Manjaro on it last year:
[2023-11-09T08:41:33+1100] [ALPM-SCRIPTLET] Found memtest86+ image: /boot/memtest86+/memtest.bin
[2023-11-09T08:41:33+1100] [ALPM-SCRIPTLET] /usr/bin/grub-probe: warning: unknown device type nvme0n1.
[2023-11-09T08:41:33+1100] [ALPM-SCRIPTLET] Found memtest86+ EFI image: /boot/memtest86+/memtest.efi
[2023-11-09T08:41:33+1100] [ALPM-SCRIPTLET] /usr/bin/grub-probe: warning: unknown device type nvme0n1.