Backporting torch to Ubuntu 20.04

[Dima Kogan <dkogan@debian.org>]

Hello!

Thanks for all your efforts in packaging the deep-learning software. It
seems like a very frustrating thing to work on.

For a work project I need a semi-recent build of torch that runs on
Ubuntu 20.04. A quick glance at the packages tells me that there are
many dependencies that would need to be backported in addition to
libtorch itself. Before I go off and spend a lot of effort on this, I'd
like to ask here. Is this as big a project as it sounds? Are there known
backports already available somewhere? Any general suggestions?

Thanks much!