Operating Systems

• GrapheneOS is a custom ROM focused on security & privacy.

Store applications

• F-Droid is a federated application store
• AuroraStore is an unofficial FOSS client to Google Play.
• Obtainium is a package installer where you can set different sources like github apkpure fdroid (even HTML).

"System apps"

• Insular is a good sandbox where you can clone or freeze apps.
• VLC is a good media player.
• Simple Notes (litteraly it's name)
• Secure File Manager is a file manager supporting AES to encrypt files.
• Open Keychain is a PGP manager.
• Password Store is a android implementation of the unix password manager

Networking

• Invizible is a good Tor + DNSCrypt wrapper with a tunnel (VPN feature).
• Mull is a secure and privacy focused Firefox fork.
• SimpleXChat is a encrypted and anonymous instant-messaging protocol and client.

Privacy-focused clients

• NewPipe is a ad-less and lightweight Youtube SoundCloud and PeerTube client. (it's really worth it to use)
• Barinsta privacy focused Instagram client.
• NekogramX privacy focused telegram client supporting PGP.
• K9-Mail is a secure mail client supporting PGP.
• Conversations is a XMPP client supporting OMEMO encryption.
• Silence is a encrypted SMS client.