You do not even want to think to load third party firmware to a router unless you know the image will work. This is how you brick a router and unless it is one of the more common ones you will not find instructions where someone figured out how to unbrick it. Some of the really hard ones they talk about soldering wires to the main router board.
From a quick look at the specs on the router my guess is there is not. Almost any router that has a DSL modem in it nobody bothers to support. The driver you need to run the DSL modem does not meet the public domain requirement to avoid copyright restrictions....although I have seen discussion of people building their own private images from the source files for some models that have dsl...