I was notified by mail that someone left a note on my user discussion page.
I opend the mail on my iPhone and clicked the link that should open my user discussion page (Button "Nachricht ansehen" - see screenshot of Mail app): URL: https://de.wikipedia.org/wiki/Benutzer_Diskussion:Joachim_Wei%C3%9F?markasread=33503688&markasreadwiki=dewiki
Since I am on my phone, it opens the Wikipedia iOS app, and then goes to a page that seems to be the article page about a person bearing my name: https://de.wikipedia.org/wiki/Joachim%20Wei%C3%9F
But not quite: it only shows the first sentence, and then the links section. Additionaly, there is the subline "user talk", see second screenshot (inside the iOS Wikipedia app)
If I open the link in the browser (long tap, open in Safari), it shows what it should, it opens my discussion page.