I did a little digging around the modx extras site. Unfortunately, I don’t think there is an equivalent extra out there. I thought maybe splittingred might have something on his github, but looking here, theres sadly nothing. I don’t think he’s doing much developing in modx anymore. I know a lot of his other extras have either been picked up by other community members or by the modx team.
As for the errors, I think the first two errors can be ignored for now, they will need to be fixed for modx 3 though. That last error makes it seem like the docmanager class file isn’t there. Maybe there was an issue installing the extra?