Maybe Configuration Issues OpenWRT 19.07.3 and DrayTek Vigor 130 - #4 by slh ff. provides some hints (vigor 130/ t-com), while not exactly what you're working with, I would expect it to work similarly.
Maybe Configuration Issues OpenWRT 19.07.3 and DrayTek Vigor 130 - #4 by slh ff. provides some hints (vigor 130/ t-com), while not exactly what you're working with, I would expect it to work similarly.