While Valve is apparently too busy shipping the Steam Deck to provide accessories around it (still waiting for the official Dock…) users of the device are getting really creative. The latest example to date is Reddit user Ethansol9 who has 3D-printed an attachment to transform the Steam Deck itself into a steering wheel, using the gyros included in the device (he apparently had to tweak their sensitivity for it to work well).
The video shows the first version of this attachment, while Ethansol9 is currently printing in the background the second iteration. They are apparently willing to share the files for printing once the new iteration is confirmed to work well. You can refer to the reddit thread for more info. This reminds me a lot of the Wii era where people were getting creative as well with the possibilities offered by the joycons of the time.
Anyway, this a great example of how much power everyone has in their hands to customize their devices.