Officially WD does not support Plex on the single bay My Cloud units. If you want WD official support for Plex then buy a multibay My Cloud model (Mirror or higher).
Unofficially, and absolutely not supported by WD, it may be possible to run a Plex server on a single bay My Cloud unit. The directions for the first gen My Cloud unit is not the same as the directions for the second gen My Cloud unit. If you perform forum search, magnifying glass icon upper right, you’ll find numerous past discussions on attempting to get Plex running on a single bay My Cloud.
https://community.wd.com/search?q=Plex%20category%3A105
In particular see this post:
https://community.wd.com/t/using-plex-media-server-with-my-cloud/94429/13
Also note that transcoding is basically not supported (per Plex) on most of the My Cloud models.
Finally, using SSH may potentially void the My Cloud warranty as will installing unsupported modules/apps into the single bay units.
