Remember that the Play Store uses encryption to download apps to the phone. If the law is enacted then this encrypted channel will technically need to be compromised too, which Google might also object to. If Google withdraw the Play Store from the UK, then what are they supposed to do?
This law doesn't just apply to messenger apps. It applies to almost every single act you perform on the internet. Everything will be mandated to be broken, including your browser. If you run a web server using https, you'll be breaking the law. If you ssh to another computer over the internet, you'll be breaking the law. If you connect to a VPN to access a work/university/school network or indeed a commercial VPN, you'll be breaking the law.
This law doesn't just apply to messenger apps. It applies to almost every single act you perform on the internet. Everything will be mandated to be broken, including your browser. If you run a web server using https, you'll be breaking the law. If you ssh to another computer over the internet, you'll be breaking the law. If you connect to a VPN to access a work/university/school network or indeed a commercial VPN, you'll be breaking the law.