Note that this page triggers a download - which is quite rude on their behalf - apparently there's no page on their site where you can read about the browser before deciding whether you may want to download it.
If you write an app that references that link, Apple will not approve it for the App Store (less of a requirement for Mac, than iOS).
I ran into this with Zoom. If you follow a Zoom conference link, it automatically starts downloading the Zoom client. I wrote an app that helps folks find Zoom meetings.
I was forced to add code that intercepts callouts to Safari, that access Zoom conferences, and show an alert, instead, asking the user to download the app.
https://duckduckgo.com/duckduckgo-help-pages/get-duckduckgo/...
https://spreadprivacy.com/duckduckgo-for-mac-open-beta/
https://duckduckgo.com/app (this one detects your device so only works if you're on a Mac)