People with ADHD can only work on tasks if they are one of the following:
- Urgent
- Interesting
- Novel
This is probably why Habitica fell off for you. The novelty wore off.
I myself have had decent success with the 'Pomodoro' technique (work for 20 minutes, break for 5 minutes. Repeat that 4 times, then have a long break). Alternatively, perhaps you could add 'urgency' by setting a daily alarm which means you have to clean right then?