I am looking for ways to import the report by REST API (with signed URL) to Qlik Sense but no clues.
On the other hand, I have tried to use Data Transfer to BigQuery. It costs a lot as each install report of an app costs. (Trying to find a way that will be free or charging only one app)
I have also tried to transfer the data from Google Cloud Storage. However, it did not succeed as the files are not changed from utf-16 to utf-8.
I have searched for documentations and tried different solutions. Still, no clues.
Have you tried to use Qlik's own REST connector to achieve what you want.
The functionality is described here Create a REST connection
You mentioned trying to transfer from BigQuery, again there is a Qlik BigQuery connector see this Create a Google BigQuery Connection
You also have the choice of using Qlik's Data Transfer tool explained here Qlik Data Transfer.
Lastly importing from Google Cloud storage is also possible using the Qlik Google Cloud Storage Web Storage Provider Connector