highly-secure versions of Android

Wikipedia:

• GrapheneOS
  • Available only on Pixel phones and tablets.
• CopperheadOS — It hasn't released any updates for 2 years, and is currently lagging quite a bit on which Pixels it supports.
  • Available only on Pixel phones and tablets.
• LineageOS — TODO: Does this focus on security and privacy?
• CalyxOS — Development is currently paused.
• DivestOS — No longer updated.
• /e/
• List of custom Android distributions

Operating systems elsewhere:

• Rentai

Other things:

• https://profilence.com/2025-04-23-why-hardened-android-devices-need-a-new-approach-to-software-quality/
• https://security.utexas.edu/handheld-hardening-checklists/android

Now, something completely different: Striped down phone hardware

Phones that can only call and take photos

• Light Phone

Lists at:

• https://www.vice.com/en/article/best-dumb-phones/
• /r/DumbPhones