Remote acces with GIRA S1 and Android Home Assistant APP

Hello everyone,
I need some help with my remote access from my smartphone. In particular with the Home Assistant APP

As a brief to my structure. I have a KNX installation in combination with the Home Assistant. I installed a GIRA S1. This makes the tunnel between KNX and Home Assistant. The GIRA S1 also provides me with a secure remote connection from the Internet to all web-based interfaces in my network via a server in Germany. So also on the frontend of the Home Assistant. There is a remote URL for this which I have to enter, similar in principle to the Home Assistant Cloud.

So far so good, if I do the whole thing on my smartphone with Google Chrome or Firefox, it works perfectly. However, when I enter this URL in the Home Assistant app, it always automatically opens Google Chrome. Once I managed to get it working in the app. But I have no idea how.

Does anyone have an idea of what that could be?