Android 11: Open HTML folder from Nextcloud in Browser

I have a folder containing an HTML file structure, which I am syncing to several devices, some of them running Android.

Syncing all the files works flawlessly, what I would like to do now is open this in a Browser (preferably Firefox) on Android devices. This should not only open one HTML file at a time, but provide access to all resources in this folder, like CSS files and images as well as all the other HTML files so I can use links between those files.

On Android 10, I found a way: I need to use quite a long URL in the browser, like file:///storage/emulated/0/Android/media/com.nextcloud.client/nextcloud/user@domain/Folder/index.html

Unfortunately, this does not work on a new tablet running Android 11 - it seems Google has made the system more “secure”. :frowning:
I also tried configuring my Nextcloud app to use the other possible folder locations, but none of those worked for me.

Is there any way I can still use Nextcloud to synchronize my HTML files and use them in a Browser?

Thanks in advance for all hints you may be able to give me!