I grabbed a couple of these, one with NAND flash and one without. Both have Wifi/BT/POE support, and I bought the POE hats because that's a damn good idea.

https://shop.allnetchina.cn/collections/frontpage/products/rock-pi-s?variant=29067635458150

= OS =

I installed their provided image of Debian buster, balena Etcher'd straight onto a spare SD card and inserted. Used adb shell to get initial connectivity to set it up and inspect things.

The root filesystem is all of ~500 MiB, which is great for compactness and speed. It auto-grows on first boot by the looks of it.
{{{
[   11.091476] EXT4-fs (mmcblk0p2): resizing filesystem from 199161 to 7835148 blocks
[   11.518063] EXT4-fs (mmcblk0p2): resized filesystem to 7835148
}}}

== Disk usage ==
{{{
root@rockpis:/# df -hl
Filesystem      Size  Used Avail Use% Mounted on
udev            210M     0  210M   0% /dev
tmpfs            43M  296K   43M   1% /run
/dev/mmcblk0p2   30G  511M   28G   2% /
tmpfs           213M     0  213M   0% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs           213M     0  213M   0% /sys/fs/cgroup
}}}

== Block devices ==
 * mmcblk0 is the SD card
 * mmcblk1 is the onboard NAND flash
{{{
root@rockpis:/# lsblk
NAME        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
mmcblk0     179:0    0   30G  0 disk 
├─mmcblk0p1 179:1    0  112M  0 part 
└─mmcblk0p2 179:2    0 29.9G  0 part /
mmcblk1     179:32   0  3.6G  0 disk 
└─mmcblk1p1 179:33   0  3.6G  0 part 
}}}

== CPU ==
{{{
root@rockpis:/# lscpu 
Architecture:        aarch64
Byte Order:          Little Endian
CPU(s):              4
On-line CPU(s) list: 0-3
Thread(s) per core:  1
Core(s) per socket:  4
Socket(s):           1
Vendor ID:           ARM
Model:               2
Model name:          Cortex-A35
Stepping:            r0p2
CPU max MHz:         1296.0000
CPU min MHz:         408.0000
BogoMIPS:            48.00
Flags:               fp asimd aes pmull sha1 sha2 crc32
}}}

== Network interfaces ==
{{{
root@rockpis:/# ifconfig 
eth0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether 4e:43:df:6b:85:ff  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 6  bytes 752 (752.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device interrupt 26  

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1  (Local Loopback)
        RX packets 2  bytes 106 (106.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 2  bytes 106 (106.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

p2p0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether 1a:77:e9:6d:75:84  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

wlan0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether e6:a6:66:59:15:ed  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
}}}