Yes the Swagman XTC2 part # S64670 will work great in the Stealth hitch you just bought for your 2018 Audi S5 part # 391AUDA5S518.
For a similar bike rack that I think you'll like better I would recommend the Hollywood Rack Trail Rider part # HR200Z as it's much more stable in the hitch on the road due to tighter clearances. . view full answer...