The Magnum Opus of this repo is certainly the AlertMe driver section. All of the Zigbee, none of the standards. This stuff was on sale before the book was written. Grab yourself a Hubitat C7 or earlier and your AlertMe / Iris V1 gear is back in action.
For everything else, just click on the driver directory and there may be some documentation. Otherwise it'll live on the post on Hubitat Community forum. You can check BirdsLikeWires activity on there for the latest.