When trying to develop a Delta Live Table-pipeline with my very generic clusters (runtime 14.3 or 15.4 LTS), I get th following error:

The Delta Live Tables (DLT) module is not supported on this cluster. You should either create a new pipeline or use an existing pipeline to run DLT code. 

My completely identical cluster using runtime 13.3 can import DLTs. But on Runtime 13.3 I can't improt helper modules when using Git-folders

Databricks Runtime version upgrade required
Please upgrade DBR version to 14.3 or above to execute commands on notebooks inside Git folders.

I cannot find anything in the documentation to provide me with assistance on how to actually solve these problems. Any help is appreciated.