So, for example, the LineageOS team introduced Lineage 18.1 based on Android 11 for a number of legacy devices. According to XDA-Developers, among them you can find the Samsung Galaxy Note 3, released back in 2013. At the same time, the brand new Android became available Galaxy S5 (released in 2014) and Xiaomi Mi A2 (released in 2018).
Note that in this case we are talking directly about the assembly from the firmware developers. This ensures greater stability and better system performance.