TP-Link Archer C20 v1 EU recover to stock firmware

Hello Everyone,
Today I Installed OpenWRT on my Archer C20 v1, hoping that it would bring me more to do with my router. However, I think that I might have installed a wrong image from the Device Page. Under the Section "Using TFTP" there was a Dropbox link that I downloaded a bin file from. I flashed this using a Ubuntu host and TFTP. However, after the installation, I could not open the configuration Interface as my browser only shows me an empty folder index. Logging in using ssh, the /www folder is empty.
I read again, more carefully, and noticed that there was a banner with the current download version. However, it seems like with the same Setup as before, they do not flash through TFTP.
In some other thread, I read about TFTP files needing a special name to flash, which is why I retried flashing the stock firmware from TPLink and the OpenWRT binary after renaming them ArcherC20v1_tp_recovery.bin.
However, it seems like I can neither get the firmware from TPLink nor the current OpenWRT image to flash using TFTP.
The router does not seem to be bricked, as it rusn fine on OpenWRT, just the user interface is missing and opkg is broken because it is too old to update the package index.
I would like to return to stock firmware.