I just read this blog post: https://blogs.unity3d.com/2019/09/11/speed-up-your-team-with-the-unity-accelerator/
It says that the accelerator supports 2019.3 or higher. Does it mean that it doesn’t support 2018.4 LTS?
That is correct. The Accelerator has Editor-side components that were only available with the 2019.3 release (alpha 9 or later), specifically centered on the brand new Asset Import Pipeline that provides much more deterministic behavior.