Lately I've been using OpenWRT firmwares on TL-WR840n in a building (aprox. 110 apartments) from my company¹. The main goal was to use Ansible to keep all the routers up to date and to do maintenance remotely. After burning all of the firmwares into the 100+ routers and testing it in production, we've seen a lot of costumers not happy about the Wi-Fi performance (wich is known to be bad, due to mt76x8 driver, I've seen this issue here already). So, due to bad performance, we're taking the routers back to TP-link firmware. Unfortunately, the only way I know of return them to the previous firmware is by Recovery mode, where the router needs to be plugged into a TFTP server via Lan port, and then turned on while holding the reset button.
So, the question is: Is there a way to reverse them to official firmware ONLY using SSH via Wan?
¹ - It was a bold project and went quite wrong, but I learned a lot from it. So, feel free to ask me about it.