Is there any open source tool like Power BI or Tableau that works well with IRIS? Thx!

Does your IRIS license include InterSystems BI (DeepSee)? In that case you can use that.

Depending on what exactly do you want to do, KNIME might be a solution (if you're ok with self-hosting HTML files  as KNIME server is a commercial product).

But most BI tools are proprietary. Any tool which support xDBC datasources can work with InterSystems IRIS.