Uno^3 is playable on BlueMaxima's Flashpoint, an archive of tens of thousands of flash games. The steps to setting it up can be found below

1. Download Flashpoint 10 Infinity from the official website
2. Extract to your desired location
3. Launch the application with the 'Start Flashpoint' shortcut
4. In the Search bar at the top left type Uno^3
5. Click on Uno^3 and Click play.

Happy Speedrunning! :)