Hi Ringo,
Can you try below approach.
Create a new UI component and a new view. And link that UI component to the navigation bar.
Now in the .htm page of the view use below code to open the UI5 application.
window.open("URL"); // here URL is the UI5 application URL
By using this approach you can load the UI5 application in the view of the Uicomponent. And the Navigationbar will also be displayed.
Kindly let me know if it helps.
Br,
Navn