Where is the authoritative or best place to find user drivers?
A place where we can all collaborate and help each other write new and better drivers? Ideally a github/gitlab repo or similar public spot that can be branched/forked with MRs back to the mainline directory.
Also, can we look at the built-in device drivers as examples on how to write drivers that will be accepted in a future hub update?
There is no one place, but if you search on here there are a few lists that have tried to compile some of them into one place. Other than that most authors post a thread in these forums when releasing a driver, so a lot can be found on here by searching.
Previous attempts to make a single place for user code have not received much support by the user development community.
No, they are closed source. That said, there are a few driver examples on Hubitat's github.
Thanks Jason. I'll probably start one then and copy over what I find with references back to the original developer.
EDIT: It depends on what you mean by "I'll start one". There are already threads on here trying to consolidate things, I don't know that another one is needed.
And if you mean compile them on github or something, I wouldn't do that. Many authors would not welcome their code being replicated in another person's github...
It would be nice if Hubitat Company would start a user repo and add some moderators. That way we could all rally around the same code.
Yes it probably would be nice - and there is a Hubitat public repo out there already for that exact purpose.
However, many/most developers chose not to use it, for various reasons. Can build anything, but you can't make them use it if they don't want to...
Hmmm... I'll apply my new/naive energy while it lasts in that direction 
It was intended to be A) the place to find Drivers and Apps or alternately, a pointer to an individual's driver/app. And B) a starting point for New Owners of a Hubitat. But with only 32 repo's the uptake isn't very large. 
Don't let me discourage you, though! If you can get people to voluntarily use it (without rehosting their code in your own git), have at it!
There are definitely some pros to that solution. It would have made my journey into development easier, I'm sure.
Download the Hubitat app
