Standard Debian; select what you want when you run: sudo tasksel

If there is nothing in /boot at all then its content is probably in another partition which gets mounted while booting. You will need to find that partition and mount it in your PC to modify it.

Yeah, it makes sense, sadly. The NanoPi R76S has Realtek NICs, but PHC support isn't included into the mainline kernel. The out-of-tree r8125 driver is... let's just say it's not very stable. The in-kernel driver doesn't display PHC at all, so it's not surprising that ethtool -T doesn't show anything. If you're noticing missing MACs and PHC vanishing after a reboot with r8125-9.016.01, it's generally because the driver and kernel versions don't match. That driver is quite sensitive to the internals of the kernel, and things become strange very quickly if udev or the DT bindings don't match up. It's also important to note that even when PHC works with Realtek, it's frequently not fully developed. For example, timestamping could be there, but it won't sync well with ptp4l, particularly when the system is under a lot of demand. So, for PHC accuracy and stability, this board was never meant to be used for serious time sync. In short: No PHC support for mainline kernel out-of-tree r8125 is unstable and breaks easily R76S hardware isn't very good for precise timing. If PHC is a must, Intel i210/i225-based NICs will work considerably better for you. Realtek + PHC is like being in agony mode.

Same problem here except there's no Desktop option. Only these: - Kernel - Storage - Access - User - Updates Got any other solutions?

You can't truly "force" the boot sequence on Helios64 since U-Boot already checks SD, eMMC, and SATA. The SD card isn't bootable if the eMMC is still booting. Things to check quickly: SD must contain a properly written raw Armbian image (dd / balenaEtcher). You can't copy files. Check that it contains a bootloader and not simply an ext4 partition. Before starting, turn off the power completely (warm reboots might disregard SD). Once the computer has started, use lsblk -f to inspect the layout of the devices. On Helios64, the mmc numbering does change, therefore tools may conceal devices to save the live rootfs from being destroyed. If you want to be 100% sure, unplug the eMMC for a short time. If it boots, the SD is OK. The boot sequence isn't the problem; the SD image is.