Finally, I got it working.

First, as suggested in the previous answer, I simplified my intent-filter. However, I didn't use the suggested one, since it seems that wildcards are not allowed in android 15 intent-filters. So, I used mimeType, as follows:

      <intent-filter>
        <action android:name="android.intent.action.VIEW" />
        <category android:name="android.intent.category.DEFAULT" />
        <category android:name="android.intent.category.BROWSABLE" />
        <data android:mimeType="application/gpx+xml" />
        <data android:scheme="content" />
        <data android:scheme="file" />
      </intent-filter>

Then, the key is, also as suggested in the previous answer, to uninstall and reinstall the app after making changes to the manifest, so that such changes take effect.