Overview
STM32F107 RBT6 + QCA8337 AL3C based router with serial and swd headers
• https://www.st.com/en/microcontrollers/stm32f107rb.html 
Mainstream Connectivity line, ARM Cortex‑M3 MCU with 128 Kbytes Flash, 72 MHz CPU, Ethernet MAC, CAN and USB 2.0 OTG
Firmware
According to https://wiki.mikrotik.com/wiki/SwOS/RB250_RB260#Summary 
new RB260GS (CSS106‑5G‑1S), new RB260GSP(CSS106‑1G‑4P‑1S) supports SwOS v2.0 and newer.
Example working (as of 2018‑07‑06) url download links which work for CSS106‑5G‑1S:
https://download2.mikrotik.com/swos2/css106/swos‑css1061g4p1s‑2.0.bin 
https://download2.mikrotik.com/swos2/css106/swos‑css1061g4p1s‑2.2.bin 
dpavlin@lib10:/lib10/arh-hw/backup/Mikrotik-RB260GS-CSS106-5G-1S/rb260gsp$ md5sum *
bf110ca7e1cd0558cefeacd9e0b62c19  swos-css1061g4p1s-2.0.bin
a491bbf2732937839e6a8222a876cc7a  swos-css1061g4p1s-2.2.bin
f098106dfc8ac5ad0fedf0181c68d8de  swos-css1061g4p1s-2.3.bin
f4f74f697039a83baa99d37017251805  swos-css1061g4p1s-2.4.bin
90d2ec8571dd9d9aeab1bfbaaa99dea2  swos-css1061g4p1s-2.5.bin
a7f046fc8a12b5ebeb85f9a4bb0dd275  swos-css1061g4p1s-2.6.bin
a1e7adc6ad63e5560156b0f2b6f272ce  swos-css1061g4p1s-2.7.bin

https://mikrotik.com/download  (SwitchOS) latest version:
https://download.mikrotik.com/swos2/css106/swos‑css106‑2.13.bin 
version
from web interface
Firmware
Current Installed Version       2.7 (built at Fri Dec 15 2017 09:42:48 GMT+0100 (CET))
Latest Available Version        2.7 (built at Fri Dec 15 2017 09:42:48 GMT+0100 (CET))

reset
• hold reset while poweron
SwOS v2.x ‑ RB260GS(CSS106‑5G‑1S) and RB260GSP(CSS106‑1G‑4P‑1S)
The new RB260GS(CSS106‑5G‑1S) and RB260GSP(CSS106‑1G‑4P‑1S) has built‑in backup SwOS firmware which can be loaded in case standard firmware breaks or upgrade fails:
Holding Reset button for few seconds while device is booting resets configuration and loads backup firmware SwOS 2.0p.
 After loading backup firmware SwOS 2.0p it is possible to connect to 192.168.88.1 using web browser and install new SwOS firmware.
default ip: 192.168.88.1
Current Installed Version       2.0p (built at Fri Oct 21 2016 10:18:39 GMT+0200 (CEST))
Latest Available Version        2.7 (built at Fri Dec 15 2017 09:42:48 GMT+0100 (CET))

After this, router knows that there is new version, but can't download it from http://upgrade.mikrotik.com/swos2/css106/swos‑css106‑2.7.bin 
Linux setup
dpavlin@x230:~$ sudo ifconfig enp0s25 192.168.88.240

wget --http-user=admin --http-password='' 'http://192.168.88.1/!stats.b'

find on network
https://forum.mikrotik.com/viewtopic.php?t=162881 
https://wiki.mikrotik.com/wiki/MAC_access 
MNDP frames
sudo apt install mactelnet‑client
dpavlin@klin:~$ mndp
Searching for MikroTik routers... Abort with CTRL+C.

IP              MAC-Address       Identity (platform version hardware) uptime
192.168.88.1    c4:ad:34:47:12:91 MikroTik (MikroTik 2.7 CSS106-5G-1S)  up 113 days 4 hours
10.60.0.1       d4:ca:6d:1:4c:ed  ccr (MikroTik 6.46.6 (testing) CCR1036-8G-2S+)  up 113 days 4 hours  XYIT-4UTW bridge60/sfp2-60