You can't use DD WRT on the homehub, it isn't available for it. But you can use the homehub as a repeater although it will have to be wired and it will have a different SSID. I used the following instructions to successfully set up a homehub 3 as a downstairs wireless repeater connected by homeplug to another homehub 3 upstairs in my local pub. Reason was a very thick concrete ceiling that blocked a lot of the signal from upstairs!
Dell XPS 13 9370 (2018) review