My workplace is also pushing long-term for Power BI (and/or some kind of Amazon tool attached to an aws data lake), but you are right, it's not nearly to the level of Tableau. My office will be sticking with Tableau for the foreseeable future.
I also have a lot of interest in the open source space. In addition to Apache SuperSet, I'm keeping an eye on the development of both Grist and Redash. Depending on community interest and support, I see these becoming potential open source alternatives to Tableau. I currently self-host Grist and am quite impressed with its potential.