You can change the default browser on your iPhone, but you still can't change the default maps app—at least, not officially. This is annoying for those who prefer using something like Waze, which has superior traffic data and a slew of other features. If you get a navigation link in iMessage, it's going to open in Apple Maps, and if you find one in Google Search, it will open in Google Maps. But as it happens, there is a way to make any maps link in Safari open in the maps app of your choice.
This is possible thanks to a simple Safari extension called Map Redirect for Map Links. With this app setup, any link can open in Apple Maps, Google Maps, Waze, Bing Maps, or HERE WeGo Maps. If you like different maps apps for different purposes, you can set the extension up so it asks you which app to use every time.
How to set up the Map Redirect Safari extension
Start by downloading the Map Redirect for Map Links app from the App Store ($1.99). When you open the app, it will give you directions to set it up in Safari. To enable it, open Safari and tap Aa after opening a web page. Choose Manage Extensions at the top, and enable Map Redirect.
Back in the Aa menu in Safari, tap Map Redirect to customize the app. Here, you can choose your target app, so any maps link opens in that app by default, or you can configure the extension to ask you each time to tap on a link. This is a good idea if, say, Apple Maps is your default, but you use Waze occasionally to check for traffic on longer routes. If you ever feel like switching default apps, you can jump back into these settings at any time.