Warning: The Google Nexus 5 is no longer maintained. A build guide is available for developers that would like to make private builds, or even restart official support.
The note above states that custom ROM development ended with LOS 14.1.
The lineage OS 17.1 - List Of Official Supported Devices neither official LOS 16.0 nor LOS 17.1 names ROMs for “hammerhead”:
Accordingly, you will’ve to settle for UNOFFICIAL variants of LineageOS 16.0 and 17.1 ROMs.
In my estimation, due to the state of affairs, /e/ support for Nexus 5 “hammerhead” will be discontinued soon.