I don't think either of these are perfect, but they both offer really good, actionable advice. The philosophies/systems described in these two don't naturally mesh, and I think that's a plus. Every GM needs to figure out for themselves how to prepare to run a game, because the things each GM needs are unique. I think having two books outline pretty drastically different approaches can help you triangulate your own needs and methods
I was a bit bummed to see that Mike didn't mention any of the Fediverse options but honestly Lemmy and kbin are still cooking as technologies so I don't exactly fault him. I was surprised to hear him skeptical of Patreon—the same incentives are there, surely, but I wasn't aware of any recent actions they had taken.
Replacing Discord will definitely be painful if/when it comes.
I found my two groups (both online, play vis VTT) through the /r/lfg community on Reddit. Not sure where I would look now.