F-Droid is a great open source alternative to the Google Play Store. To quote from the F-Droid website:

What is F-Droid? F-Droid is an installable catalog of FOSS (Free and Open Source Software) applications for the Android platform. The client makes it easy to browse, install, and keep track of updates on your device.

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Many of the proprietary apps you are currently using have alternatives on F-Droid, which won't secretly track you or steal your data. Some of them may not be as polished as their closed-source alternatives, but it is a small price to pay if you care about privacy and security.

If you want to read more about why you should be concerned about privacy and security you can check out this article about how Google may be tracking your location and this longer article on, what it calls, the Age of Privacy Nihilism.

Some of the apps contained in the F-Droid app store require your phone to be rooted. Since rooting your phone is only recommended for advanced users, the apps listed below do not require root. These are, however, just our recommendations, and we encourage you to check out the app store yourself to see if there's something in there that you would consider using.

Media

  • NewPipe: This is a great app that lets your watch YouTube videos without being logged in and getting tracked.
  • AntennaPod: Polished app, easy to use, with lots of methods for adding podcasts to your library.

Communication and Social Media

  • K-9 Mail: Very reliable email client that you can even connect your gmail accounts to.
  • Signal: Secure messaging, but only works if your friends have it!
  • Riot.im: Another secure messaging app, which is somewhat more complicated than Signal but also allows your to set up an account without it being attached to a phone number.
  • Mastadon: Twitter alternative with a somewhat high learning curve since it is a decentralized network. Check it out, you might like it.

Productivity

  • Nextcloud: Alternative to Google Drive and other cloud services. Nextcloud is much more than simply cloud storage, however. Open Wave Digital uses Nextcloud for project management, to-do lists, calendar events, and even collaborative editing.
  • DAVdroid Sync: With DAVdroid, you can sync your Nextcloud services to your android phone such as calendar, tasks, and contacts.
  • Etar - OpenSource Calendar: Etar can be used as a calendar by itself, or it can be synced with your Nextcloud calendar using DAVdroid.
  • Tasks: The same goes for Tasks, which can just be used locally, or, otherwise, synced with your Nextcloud tasks.

Privacy and Security

The standard F-Droid repository has many privacy and security focused apps, but for even more options, you need to make sure the Guardian Project repository is is enabled.

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With the Guardian Project repo enabled, you can now browse their apps in F-Droid.

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Some of the privacy and security apps we recommend are:

  • Orbot: This app connects your phone and all its communication to the Tor network.
  • Orfox: A browser you can use in conjunction with Orbot.
  • Scrambled Exif: For removing metadata from your images before uploading to the internet.
  • Duck Duck Go Privacy Browser: A nice browser that respects your privacy.

Other F-Droid Configuration

The configuration and settings menu in F-Droid is quite long and allows for a lot of flexibility in terms of how far you are willing to go (or how much inconvenience you are willing to accept) in securing your phone. There is even an "Expert mode" for advanced users. Below is an example of some of the privacy settings which allows you to run F-Droid through Tor, as well as prevent screenshots while in the app.

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Next Steps to Secure your Android Phone

Check out this article on Android Security by Gadget Hacks on how to stop Google from tracking you (to an extent). This guide by Android Authority and this other one by Lifehacker are also both pretty comprehensive!