Re-Flash SamKnows TP-LINK TL-WR741ND v2.4

(Writing this up for myself) As i joined the SamKnows EU ISP test, i received a TP-LINK TL-WR741ND v2.4. When i upgraded our internet connection after some time, we received a new SamKnows-box that apparently was necessary to monitor the new faster connection. Since returning the TP-LINK TL-WR741ND v2.4 would be relatively costly, i could keep it. But it came with a tweaked firmware, so i could not re-use it without replacing the firmware.

So i was happy to find this article describing how i could flash another firmware. But when i tried from my Macbook with OSX 10.11 El Capitan, i had trouble accessing the Macbook once i telnet'ed into the router.

Some things i found:

• FTP is by default disabled on 10.11 ... to enable it, i used FTPd enable from Troncept.
• I also had trouble to find out where the file i wanted to transfer from the Macbook to the router, had to be located. When wget'ing a file from an ip, i found out you can (should?) specify the user-account (like so: "wget ftp://:@/"), and in the home/root of that user, the file is looked for. Probably unnecessary, i created a temp user, and allowed ftp-access following this article .
• At one moment, while telnet'ed to the router, i wanted to list all the files on the 'remote' machine (which, from the router point of view, was the Macbook ... i hoped, when listing the files, i could verify in what folder the router was looking when executing commands), so i found you can list this with ssh
• But before i could use SSH, i had to enable it on the Macbook
• I tried the Gargoyle firmware as mentioned in the first article, but i had very bad and flaky performance ... but now i knew how to flash new firmware, i tried some more files (amongst which were openwrt ones) ... i had some problems accessing web interfaces, at some point i even was unable to ping the router ("ping: sendto: No route to host"), and when i had problems accessing the router via Telnet i found newer versions of OpenWrt don't have Telnet-access anymore (got "telnet: connect to address 192.168.1.1: Connection refused - telnet: Unable to connect to remote host", but this article helped me access SSH), but eventually ended up using the official TP-LINK firmware
• Possibly what was needed (and maybe i did not to that often enough) was the proper 30/30/30 hard-reset
• Unexpected: when i did "ssh 192.168.1.1", i got "The authenticity of host '192.168.1.1 (192.168.1.1)' can't be established. RSA key fingerprint is SHA256:. Are you sure you want to continue connecting (yes/no)?". I had read using SSH could take complex key management, so i was surprised when, after i replied "yes" i was greeted by a BusyBox message ... (after which i replaced the firmware that was flashed at that moment by the official TP-link firmware).