I am building a music playing app using Flutter. It helps me as a single developer to build an app once for both platforms. However there are a few hiccups I have hit on bot
You just need to enable "Audio, Airplay and Picture in Picture" in Xcode as shown below. You need to add the Capability "Background Modes". You can find this in the "Signing & Capabilities" tab:
A detailed instruction you can find in the offical docs: https://developer.apple.com/documentation/avfoundation/media_assets_playback_and_editing/creating_a_basic_video_player_ios_and_tvos/enabling_background_audio