In 2017 or even also 2016, a refurbished Asus Wi-Fi AC router was talked about and searched repeatedly because not only is it a certified refurbished Asus AC router with cheap price but also it could be flashed to a real ASUS RT-AC68U router. There are multiple websites have provided flashing guides.
This refurbished router is T-Mobile TM-AC1900. It was also a hot deal on Amazon US since the reason of flashing to an ASUS router. The lowest price were $47.99 USD. There were also many Canadian ordered this item because its price was so cheap that even with shipping cost it was still cheaper than buying the same router locally in Canada.
However, in a night of March 2018, most of flashed TM-AC1900 routers got problems with the firmware was reset back to the original T-Mobile Firmware automatically!
The reason was because Asus used their new firmware (Version 18.104.22.168.384.20624) to disabled AiMesh functionality completely on all T-Mobile TM-AC1900 routers that have been flashed to a ASUS RT-AC68U. If anyone tried to reinstall the updated firmware manually then the router will be reset to old TM-AC 1900 firmware again.
Even there were several work-around methods soon later, but since ASUS officially start to tighten up on the TM-AC1900, so obviously this refurbished Asus router is no longer a good deal, unless someone can find a better way to flash it in some day. But for now, we’d better to avoid buying any TM-AC1900 router.
What we suggest is that just buy a formal Asus AC68U directly, even its price is more expensive, but your time is still money.