Beginners way to try OpenWrt on a Speedport 921v?

I just want to check to not give up too soon:

I have a Speedport 921v. It has no use at the moment for me. So getting to know openwrt would give the device a reason to be.

Reading this (Lantiq XRX200 Easybox 904xDSL and Speedport W 921v build) I had the hope that there would be an easy way to install a working version of OpenWrt on this device - but all the files there seem to be offline.

The Table of Hardware lists this device, but doesn't offer a factory image.

So my only chance would be to understand and follow the guide given here?

I'd say so...

O.K., thanks for confirmation.
I have to give up when there is talk of a serial cable, I don't think that I own such a thing and buying a cable for loosing wlan doesn't seem to be a good start.

I fear I am better off buying a cheap device knowing to be supported by openWRT and give the 921v to a recycling station.