This extension allows the voice to be slowed down inside the Chrome browser. The downside is that it only works on web pages with highlightable text, so you can’t say, highlight text in LR’s read mode and have it read to you:
I’m going to use this to get some listening practice with text on web pages that don’t have audio provided for accessibility until LR can give a reader dial (see above link in my other reply)/audio speed selector in the text/read mode—rather than relying on the LR reader for sentence audio.
P.S. Only allows for 5 minutes of free daily listening with what they call “premium” voices 
But, they have free voices available that don’t seem to have a time limit.
P.P.S. Similar to the voices in LR’s text mode, voices used in the Microsoft Edge browser sound better (than in Google Chrome) with this extension.