In the past, I have had make a good number of Power Point presentations. I could edit them with a screen reader, but I could not have any of them speak the presentation as I used it. I then found a small free app called Power Talk. It would speak each slide as it was presented. It would even read alt tags with descriptions of graphics.
It started as a project on Source forge. I can still find it, but it will not work with Power Point 365. It is not clear if it is the program or Windows 10 that are the culprit. Does anyone on the list know of a similar app?