Essentially it’s all there in the question. Are they pulled from the official Ubuntu images found on dockerhub (https://hub.docker.com/_/ubuntu?tab=tags)?
There are many tags, and the ‘tag’ section of each pytorch / container does not indicate more than a hexidecimal reference to some container without additional information (that I can understand, anyways - perhaps the hexidecimals are a specific reference I should know how to interpret - If so let me know!).
If there’s dockerfiles to look at that’d be helpful too, but I’m more curious about just knowing what the base image is starting from.