Update file extension for SharePoint Online

We have our training files in SharePoint.  Previously, we were able to modify the file extension for our index.html file to index.aspx, via SharePoint Designer. We just migrated to SharePoint Online and have lost that functionality.  Is it possible to use Power Automate in a similar way, to modify the file extension?  

 

The goal is to be able to play the .aspx training file when it's clicked on from the SharePoint libary.  I did an initial test, but the .aspx file downloads rather than play the training file.