Breathe new life into your old smartphone: The TWRP recovery image and the free Android offshoot LineageOS let you install the latest security updates every week.
Every mobile device needs its own Android build because of numerous drivers that are not available in the source code. The need to maintain every version of Android for every mobile device means that many manufacturers eventually stop supporting updates. Often, smartphones or tablets that still work perfectly can no longer be used without worry because the manufacturer has simply ceased to offer bug fixes and security updates.
The fact that many drivers for smartphone hardware are not available as source code makes it difficult to provide Android upgrades. The LineageOS project , the successor to the CyanogenMod project, which was discontinued in 2016, proves that it is not impossible to keep these devices up-to-date. Unpaid volunteers at LineageOS do the work that many manufacturers do not want to do: They combine current Android releases with the required device-specific drivers.
The LineageOS project (Figure 1) provides Android systems with a fresh patch status every month for around 300 devices. The builds are released weekly, unless there is a problem during the build. The Devices page on the LineageOS Wiki  provides the details of whether a LineageOS build is available for your smartphone or tablet.
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