You're severely misunderstanding what is going on here.
Many TP-Link routers will try during bootup to contact a TFTP Server for new firmware. The S4 doesn't do that.
The S4 has the HTTP recovery with that nice webpage where you can select a firmware file and upload it.
Instead of a firmware file you upload the exploit.
And while the bootloader is checking the file. the exploit breaks out of that and executes bootloader commands.
And those commands are then using the tftp client of the bootloader to get the firmware from your tftp server and execute that.
At no point do you need a firmware recorvery tool from tp-link nor is any tftp guide for other routers going to work.
The steps at https://openwrt.org/toh/tp-link/deco_s4 are correct. If they don't work on your router then you've likely got one where TP-Link updated the bootloader to prevent the exploit from working....or you did it wrong.
Maybe these instructions are clearer to you. But keep in mind that they're for the M4, not S4, and you need to of course use the firmware files for the S4. But other than that it should work the same: