there are lots of good kart racing games you can play on your steam deck, but also lots of terrible ones. most would agree that you can skip garfield kart, and the sequel.

besides mario kart, which you can play on the steam deck using emulation, you can check out the sonic racing series:

• Sonic & Sega All-Stars Racing
• Sonic & Sega All-Stars Racing: Transformed
• Team Sonic Racing

Some other noteworthy kart racers on steam:

• Meow Motors
• Super Indie Karts
• The Karters 2: Turbo Charged (currently in beta)
• KartRider: Drift
• Disney Speedstorm (this one has mixed reviews)

if only they had a way to properly track blue coins