Mobile Linux operating systems have experienced an enormous upswing in recent years due to the development of Linux smartphones like the PinePhone and the Librem 5. Around two dozen Linux smartphones exist today, and you can find the 15 most important operating systems on the ISO of a multi-distro demo known as Megi's multi-boot image [1]. Fragmentation in the mobile Linux operating system niche is high, but there is also some cross-fertilization in the scene.

The incentive is the desire to counter the duopoly of Android and iOS with something that open source enthusiasts can use without hesitation. The goal is also about sustainability. Frugal users believe that mobile devices need to be supported for ten or more years, instead of dropping out of the update process after two years, as is usually the case with Android, and ending up as hazardous waste. Mainlining [2] is an important keyword here – the term refers to the process of replacing the supplied kernel with a kernel that corresponds as closely as possible to the mainline kernel at kernel.org.

At the center of this development is the open source project PostmarketOS (PMOS) [3], founded in 2017 as a fork of the minimalist Alpine Linux distribution [4]. PMOS supports several user interfaces (Figure 1), including KDE Plasma Mobile, Unity 8 (the UI now known as Lomiri), Purism's GTK-based Wayland Phosh interface developed for Librem 5, the tiling compositor Sway, the Suckless-based Sxmo, Gnome, Mate, and Xfce4. Devices like the PinePhone or the Librem 5 run a mainline kernel out of the box, but the intent is for all Android devices with PMOS to operate with a mainline kernel in the long run, if possible.

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