How to generate voiceover and subtitles for a (Powerpoint) presentation

Assuming you want good audio quality and want to avoid using YouTube for the generation of subtitles for some reason (time e.g.).

Guide for those in a hurry

Make a presentation. Avoid:
1. Animations, make incremental slides for that
2. If really necessary, you should extract the animated slides to a separate presentation later and render that out as a video.
Type the Audio track in the slide notes. You can check overall length by running notes-to-wav.ps1 and loading the audio into your favorite music player, like foobar2000
Export all slides as PNGs
Use some service to generate high-quality speech from the allnotes.txt, like Play.ht
Use your favorite video editor to arrange the slides according to the audio track, fine tune etc.
Render the video
Extract the final audio track, e.g. using ffmpeg -i <video> -vn output-audio.wav
Feed it back into picovoice using audio-to-srt.py
Import the srt into the video editor
Fix subtitles and timing
Re-Export subtitles
Profit.

This script generates several things for you:

Slide[\n+].txt containing the notes text separated by slide
Slide[\n+].wav containing the text synthesized by System.Speech.Synthesis.SpeechSynthesizer - this is helpful to keep track of the total talking time mostly
allnotes.txt the whole text in a single file

This script generates a .srt from an audio track using the strategy described here