IssueTracker

From the other issue:

note that it is never the right approach to attach a <deeplink> to an <activity> destination as that will never give you the right behavior when using an implicit deep link on another app's task (where the system back should immediately take the user back to the app that triggered your deep link). Instead, you should attach your deep link directly to your second activity (either by manually writing the appropriate <intent-filter> or by adding the <deeplink> to the start destination of a nav host in that second activity).

A lint error saying as such when a <deepLink> element is added in Navigation XML would go a really long way to avoiding this case. Our guide to writing Lint checks in AndroidX is a good place to start to start a navigation-runtime-lint artifact that would contain this check.

We have some public docs on writing library lint rules. Specifically the xml lint rule part should be pretty helpful.