hello, Model: TD-W8980 Can I convert my device from adsl to vdsl, openwrt?
Yes and I've used a TD-W8980 on a VDSL connection. If your VDSL connection requires Vectoring you will have to source a vectoring capable Lantiq xDSL firmware file as the one OpenWrt can distibute doesn't include this support - I suggest you peruse this thread for more info if you need this.
It's not really a conversion since the hardware supports it out of the box. Just load OpenWrt on it and have a look at the thread @pythonic linked.
Keep in mind that the 5GHz WiFi is not supported, you will only get 2.4GHz from the Atheros chipset. More details on the wiki page: https://openwrt.org/toh/tp-link/td-w8980_v1
If you haven't yet installed OpenWrt, carefully the details on the wiki page. I remember having success with the web interface exploit method.
Looks like you can cross flash W9980 firmware to make W8980 work with VDSL, if you didn't want to use openwrt and lose 5ghz
I would like to add that for me, the web interface exploit method only worked after cross-flashing the TD-W9980 firmware.