I love the concept of gamifying real life challenges. I especially love all the science to back it up. I just wish the UI had the feel of a game. It currently is as exciting as checking things off a to do list. You get to see yourself “level up” but the levels seem arbitrary. What if you were an avatar moving through and exploring a world with different terrains/cities, etc. You could still have the same customization of making it your own journey by utilizing menus and choices as you go. When you complete a power up your avatar could get items, you could encounter “bad guys” on screen, have an option to select which of your bad guys it is, and then “battle” them (it could be a really basic animation, nothing fancy). You could select your quest and travel to different parts of the world either to complete it or when you complete it. Maybe this wouldn’t appeal to everyone, but for me, when it’s tough to get motivated, any little thing to make it more fun helps. Thanks!
Captain (not so) Calm commented
I have not played it myself, but from pictures and statements from friends it seems like Habitica (https://habitica.com/) could be what you're looking for. Though I don't know if it matches the mechanics (Power-Ups, Bad Guys, etc.) of SuperBetter. Maybe you can utilize both "games".
Personally, I like the simplicity of SuperBetter a lot. I have got sensory issues, so if it would be modelled more game-like, it would be necessary for me to be able to turn this feature off.