Hello Käy,
There is a way to download the latest 4.14.3 plugin. In the Unreal Marketplace, search for 'Substance' in the search box, then click 'Install to Engine' and select 4.14 from the dropdown menu. This places the plugin in the folder path:
C:\Program Files (x86)\Epic Games\4.14\Engine\Plugins\Marketplace
If that does not work for you, try placing the plugin in the runtime folder:
C:\Program Files (x86)\Epic Games\4.14\Engine\Plugins\Runtime
Also, as of now, only the Unreal 4.15.0.xx plugins support SD6 substances (substances using the new features, text node, curve node, etc).