I think the word abandoned here is a bit premature. People have to realize because of changes in the core of OMV a lot of the plugins were ported 2 times for OMV 3. Not fun. So I think Aaron and HK-47, who have done most of the porting, are feeling a bit burned out. After most of the plugins are ported they will probably get bored and do a few more. But some of the plugins are just not being used enough to justify them being maintained. And those will likely not be ported.
I don't see any work being done on the docker plugin as of yet. But just because it is not on Github does not mean that the person working on it has not started the porting for OMV 3.