Version 4.0 is tricky. Try Archer A6 v4.0 US firmware. If that fails, OpenWrt is your only path. Check OpenWrt forums for "Realtek RTL8197F" support.
Introduction: The Challenge of Regional Firmware tl-wdr7660 english firmware
This is where the search for becomes critical. Many users mistakenly believe a simple language pack exists. The reality is more complex. In this 2,500+ word guide, we will explain the architecture of the TL-WDR7660, the difference between hardware versions, where to find legitimate English firmware, and the step-by-step process to flash it safely. Version 4