https://www.techradar.com/news/valves-steam-link-app-wont-be-coming-to-the-apple-app-store

After its announcement for iOS and Android earlier this month and a successful Android beta, Valve’s Steam Link app will not be launching on iOS. 

Apple had originally approved the app for launch on the official Apple App store on May 7. However, the Steam Database Twitter account has posted that Apple revoked its approval of the app on May 10, just one day after Valve released the news.