Is there a way of getting data from a DataMiner System into Google Looker?
There could be a solution for your problem with the upcoming feature called "User Definable APIs". This will allow you to set up an authenticated endpoint on your DataMiner system and expose the data you would be looking for that is present on your DMS.
At the moment this feature is still under development.
I guess it would depend on the use case, and what data you would be interested in (e.g. alarm data to show statistics, trend performance data, real-time data).
Possibly the offload function of DataMiner could be considered here. Offload database | DataMiner Docs. It allows one to offload both alarm data as well as trend data. This can go into various SQL stores, or plain files, and that could be loaded into Google Looker.