Hi @andreas789 ,
Please try using XMLA endpoints or deployment pipelines to change data sources of Power BI datasets.
Using XMLA endpoints to change data sources in a Power BI dataset
Get started with deployment pipelines
And this thread is an example of changing the data source using Tabular Editor, you can refer to it.
Solved: Change Data source In Power BI Service
If the problem is still not resolved, please provide detailed error information or the expected result you expect. Let me know immediately, looking forward to your reply.
If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.