Looking to export Vega (or Vega-Lite) into PowerPoint as an interactive visualization. Are there any known libraries/techniques to do this easily? If not with Vega, are there other interactive visualization libraries you would recommend with this capability?
Interactive Vega/Vega-Lite charts are rendered via HTML and Javascript, so your question is equivalent to asking whether arbitrary HTML/JS documents can be displayed in Powerpoint. The answer appears to be yes, if you're using Powerpoint Online with the WebViewer addon; see Editable HTML, CSS and Javascript within Powerpoint Presentation?
You can create an HTML view of your chart using Vega-Embed, and then use this in the online powerpoint.