I was invited to use the Rossmann drugstore app for getting special offers and discount. However, there are 9 trackers...
Is there a safe way to use it without being tracked? In a sandbox mode?

Hi,
one method would be to block these trackers if possible.

You may look at Tracker Control (TC) on F-Droid here

Depending on how deep you want to go/fell into a rabbithole, take a look at Rethink: DNS + Firewall + VPN here

In the case you didn't heard about the signature issue currently on f-droid, please take a look at this.

    I use this app and any other comparable shopping app in the private space, which is always isolated from the rest of the OS and apps inside of it cannot do anything as long as the private space is locked.
    I have set automatic locking of the private space to 5 minutes after screenlock instead of immediately - that makes it easier to show QR codes at the cashier as you don't have to keep your phone unlocked the whole time waiting in the queue.

    Another option would be a completely different user profile, or of course the above mentioned Tracker Control.

    I don't want to start with another profile at the moment. Or would you recommend it together with Tracker Control? Is Tracker Control enough to be safe?

      Dan-cer However, TC seems to have it inbuilt.

      It uses the VPN slot. It is not a VPN itself.
      https://github.com/TrackerControl/tracker-control-android

      Under the hood, TrackerControl uses Android's VPN functionality, to analyse apps' network communications locally on the Android device. This is accomplished through a local VPN server, to enable network traffic analysis by TrackerControl.

      No root is required, other VPNs or Private DNS are not supported. No external VPN server is used, to keep your data safe! TrackerControl even protects you against DNS cloaking, a popular technique to hide trackers in websites and apps.

      To use a VPN + firewall at the same time, it would be better to use Rethink as mentioned above.

          Dumdum Thank you. I had overread that alternative and will look into it next days.

            Out of topic.
            I decided to use none of them (Rossman, Lidl, Rewe, Payback etc) just to save a few bucks.
            Privacy is more important to me.

              brandy078 That's why I rejected them for years too. Before really using them I want to make sure to avoid all tracking and other issues.
              However, if that would be to much to do with spending a lot of time, I'll continue to avoid them.

                4 days later

                hummingtop I installed Rethink as @Dumdum recommended it too.
                Have I to do some special settings for tracker blocking of Rossmann app? Or does Rethink work out of the box?

                    Dan-cer

                    Provided your VPN or DNS provider (if you have a custom one set) does filtering then it should work out of the box.

                    However if you do not have one of those set that does filtering.

                    Go to Configure > DNS > Download and Enable On-device blocklists > configure the blocklists you want to use. The basic tab for on device blocklists is pretty easy to understand. Don't enable all the lists though or you will break a lot of services. I believe the lists are color coded to imply how likely it is to break things though. Green being the safest/lowest chance of breakage.

                        Dan-cer

                        I've had issues like that before. I would suggest toggling in DNS settings "Use in-app downloader" to the opposite of whatever is currently toggled. That has sometimes helped me. It could also be some sort of connection issue but I don't see how any issue like that would apply to your case currently.

                        Do keep in mind the download might take a while depending on your connection. Like a few minutes.

                        If this doesn't work however maybe just try again later? Sometimes these problems fix themselves on their own.

                            This evening I had bad telefone connection somehow, and I deinstalled Rethink to get rid of any trouble.
                            However, I have to investigate the issue.
                            Is it possible that VPN and DNS settings can cause bad telefone connection of my sim provider?

                            Supplement:

                            After I deactivated Rethink, messages about DNS and downloads appeared every second, totaling a few hundred MB. Very strange. I had to uninstall the app.

                            I'm currently using TrackerControl again. Some trackers are displayed for the Rossmann app. Does this mean that TC automatically blocks these trackers?

                              15 days later

                              rdns dev here

                              Dan-cer After I deactivated Rethink, messages about DNS and downloads appeared every second, totaling a few hundred MB. Very strange. I had to uninstall the app.

                              You mean, the on-device blocklist files were being repeatedly downloaded? That sounds serious.

                              Which version of Rethink were you on (it'd show up in the footer of the About UI)?

                              messages about DNS

                              Can you clarify what this means?

                              totaling a few hundred MB

                              Note that, DoH & DoT are expensive in terms of bandwidth. You can expect anywhere between 5x to 50x increase in data use with DoH & DoT. We're trying to improve upon this with optimizations that we can do on the client in the upcoming version, v055o which is due in a few weeks (but I've been saying this for months!)).

                                  ignoramous I'm sorry that I can't help to figure out what caused that mass download because I immediately deinstalled the app.