I buy this kit:
MT7688 has: Ram DDR2 128 MB, Flash 32 MB, Cpu frequency 580 MHz
It comes preloaded with OpenWrt 14.07 or plain Linux.
As I don't see anybody using this kit in the forum, I would like to share my very little experience.
The first step was to update the firmware.
MT7688AN and MT7628AN chips are similar.They said:
The MT7628 series are pin-to-pin compatible with the MT7688 series. However, MT7628 comes with a 2T2R antenna, while MT7688 only supports 1T1R antenna.
So I download this image:
The serial port near the power jack give access to the bootloader at 57600 bauds, using a TTL-USB dongle. Under Windows 7 I use Teraterm. Setup for serial is 8 bit, no parity, 1 bit stop and no flow control.
Then it is easy to upload the new firmware through tftp: I use Tfpd64 under Windows 7 as a Tftp server. I connect one of the Lan port (not the Wan port) of the MT7688AN to the box. It is necessary to annotate the IP that the Dhcp server of the box assign to that port.
When the MT7688AN is booting, press 2 to load the firmware and flash it.
Now, after the reboot I am able to access OpenWrt 19.07.02 on the same serial port.
Next step will be to configure OpenWrt according to my network.