Alternatives to Droidian
A Debian-based GNU/Linux distribution that runs on phones originally shipped with Android. The listings below can replace it for an important use case. Each note says what changes if you switch.
The original
Droidian
A Debian-based GNU/Linux distribution that runs on phones originally shipped with Android.
Replacements
Listings that take over the same core job as Droidian.
Mobian
A Debian derivative for mobile devices such as the PinePhone and supported Android phones.
Mobian is also Debian-based but targets Linux-first phones such as the PinePhone as well as supported Android phones, with a limited range of supported devices.
Ubuntu Touch
A community-maintained Linux mobile operating system for phones and tablets that can act as a desktop.
Ubuntu Touch supports dozens of devices with a graphical installer, regular OTA releases and a convergence desktop mode, but uses its own app catalog.
postmarketOS
A Linux distribution for phones and other devices, built to keep hardware useful for years.
postmarketOS uses reverse-engineered drivers instead of Android components, offers several user interfaces and aims to keep phones useful for around ten years.
Sailfish OS
A Linux-based mobile operating system from Jolla that can run Android apps through AppSupport.
Sailfish OS is a paid, closed-source Linux system from Jolla that can run Android apps through AppSupport, available only for supported devices.
Also worth comparing
These listings name Droidian as their own alternative, so the relationship runs both ways.
Plasma Mobile
KDE's open-source mobile shell and app ecosystem for Linux phones, built on KDE Plasma.
Droidian runs Debian on phones originally shipped with Android using Halium and libhybris, so hardware support depends on each phone's Android components and the supported device list.
Similar software
Related functionality, not a direct replacement.
LineageOS
A community Android distribution for a wide range of phones and tablets, shipped without Google apps.
Android Open Source Project
Google's open source Android code base, which you can download, build and flash yourself.