For only android standalone app i need to update the Expo SDK version to 39: this is due for this bug App was required to update for Background Location by Google · Issue #11102 · expo/expo · GitHub.
My question is:
if i update the SDK version in app.json and i make a new standalone build for android expo build:android -t app-bundle
and i submit the binary to the Google Play i need also to make a new build for iOS too ? or the iOS app continues to operate normaly without errors ?
Since the iOS will be based on a different SDK version, it will not attempt to download the published SDK 39 code. So you should be fine.
But you might want to use different Git branches if you are planning to keep the iOS build on the older SDK and still make tweaks to the code. Also, it might make sense to use different release channels.