ssh is unlikely to be causing the problem, it comes up as standard on arch. So more likely that the network isn't coming up, so type "ip a", I'd expect it to show probably "eth0" (with a possibility of "usb0"), now that should be set "up" and configured. If any of this fails, that why you have no network.
Secure boot shouldn't be too much of a worry, secure boot is mainly an Armv8 thing, and the rk3288 is an A17 chip, and A17 is Armv7-A. So it would be surprising if you have secure boot. However even if you do, it will be the uboot that is secured. uboot though will boot whatever it is set up for. So we can just use uboot to boot arch.
Only machine I've seen so far that does secure boot, is the odroid-c2, an Cortex-A53 SBC. And that, although it has secure boot, its been set up more as a proof of concept - as payloads (e.g. uboot) can be either signed, or just checksummed; this means you can test signed payloads, but also just used checksummed payloads.
Did you dig into the device tree? I checked linus git tree, to see whats mainline. There isn't a device tree for the tinker board S, but there is one for the tinkerboard:
https://github.com/torvalds/linux/blob/master/arch/arm/boot/dts/rk3288-tinker.dtsThat loads up the rk3288 cpu config:
https://github.com/torvalds/linux/blob/master/arch/arm/boot/dts/rk3288.dtsi(Also see
https://github.com/torvalds/linux/blob/master/Documentation/devicetree/bindings/net/rockchip-dwmac.txt)
These both set up the ethernet as:
$this->bbcode_second_pass_code('', 'gmac: ethernet@ff290000 {
compatible = "rockchip,rk3288-gmac";
reg = <0x0 0xff290000 0x0 0x10000>;
interrupts = <GIC_SPI 27 IRQ_TYPE_LEVEL_HIGH>,
<GIC_SPI 28 IRQ_TYPE_LEVEL_HIGH>;
interrupt-names = "macirq", "eth_wake_irq";
rockchip,grf = <&grf>;
clocks = <&cru SCLK_MAC>,
<&cru SCLK_MAC_RX>, <&cru SCLK_MAC_TX>,
<&cru SCLK_MACREF>, <&cru SCLK_MACREF_OUT>,
<&cru ACLK_GMAC>, <&cru PCLK_GMAC>;
clock-names = "stmmaceth",
"mac_clk_rx", "mac_clk_tx",
"clk_mac_ref", "clk_mac_refout",
"aclk_mac", "pclk_mac";
resets = <&cru SRST_MAC>;
reset-names = "stmmaceth";
status = "disabled";
};')
And that looks to me like the guts of the ethernet are part of the rk3288 chip (e.g. it isn;t using an external usb ethernet).
Now this is the device tree for tinker board, looking at the hardware it *may* also work on the tinker board s. Note I haven't been able to find a tinker board s device tree. Hence why its worth checking what device tree you are using, how ethernet is set up, and what the kernel is doing with that information.
