From Google’ blog
Choice screens: Switching your search engine or browser is something you can already do easily on Android and Chrome. Under the MSCA, we will show choice screens that prompt you to select a search engine and browser. You will begin to see these on Android phones in Japan, as well as in the Chrome app on iOS phones.
Alternative in-app billing
Google already complies with many of the MSCA’s requirements. For example:
•You can already install third-party app stores on Android devices and easily swap defaults on Android and Chrome
From Apple
With the MSCA’s new requirements, developers will also have the option to distribute iOS apps in Japan using alternative app marketplaces other than the App Store. Alternative app marketplaces will have to be authorized by Apple and will need to meet ongoing requirements to serve developers and users.
Users under 18 will require parental approval to use outside payment method, while user under 13 and apps for kids will have to go trough Apple’s system.
A browser choice screen and search engine choice experience, giving users in Japan new ways to pick their preferred browser and search engine.
New options for developers of browser apps to use alternative browser engines other than WebKit, with strict security and privacy requirements.
A new API that enables developers of voice-based conversational apps to provide users the option to launch their app with the iPhone side button.