Stephenson uses Substack? I really would have imagined him using something more bespoke or Ghost.

An added benefit of moving away from Canva will be the colourspace. Canva doesn’t use CMYK (might have upgraded since the last time I checked). Making your slides with other software will make them print using the right colours.

For slides you can use Impress or Reveal.js

markdown > pandoc > reveal.js is easy, depends on what you’re doing graphics-wise in your slides

(I use LaTeX Beamer slides made with pandoc, but they’re not flashy)

Another option could be Inkscape which can make multipage documents. You can even animate them using jessyink.