At the moment on the iPhone or the iPad there is no way to switch the default apps, this is something that Apple is apparently considering.
The company is considering whether it should allow users to change the default apps for certain things on the iPhone, iPad and also their HomePod.
For example the default browser is Safari and although you can use other browsers on the devices Apple does not let you replace the default apps with alternative ones.
At the moment if you are sent a link in an email to a website, when you click it the link automatically opens in Safari, if you could choose another default browser, for example Firefox then it would open in that.
Apple is apparently also considering letting users choose the defaukt apps on their HomePod, at the moment the default music app is Apple Music, if they do thi you could then choose Spotify and others. There are no details as yet on when this may happen, as soon as we get some ore information we will let you guys know.