There is excited news for those Sharepoint developers which use Camlex in their work: now Camlex.Client library (Camlex version for CSOM) is available for each Sharepoint version as separate nuget package:
|Sharepoint version||Nuget package|
Before it was only Sharepoint Online version Camlex.Client.dll (see here). May be it is more logical to call it package for SPO version Camlex.Client.Online but since this package exists quite a long time I left it to keep backward compatibility.
So now for targeting correct Sharepoint version you may just add appropriate nuget package to your project and work with it. Each package contains Camlex.Client.dll assembly which is compiled using appropriate versions of CSOM (Microsoft.SharePoint.Client.dll and Microsoft.SharePoint.Client.Runtime.dll). This approach is similar to those which is used e.g. in OfficeDevPnP which uses different nuget packages for each Sharepoint version.
This feature is well wished feature and was requested many times so probably many developers will find it useful. The only reason which prevented me to do it earlier is that it will increase maintenance time and as I’m the only developer who maintains the project it is quite significant. But now time has come and now with each new release all 4 nuget packages for Camlex.Client will be updated.