Stheno.jl v0.7 has now been released. It is a very breaking release, in that much of the main user-facing interface has been refactored to ensure compatibility with the AbstractGPs.jl ecosystem that the JuliaGaussianProcesses org is building, and to ensure that the internals are more maintainable and understandable.
The result is a much simplified package, but you can still do all of the things that you used to be able to do, albeit the way in which you do it may have changed slightly.
Please check it out, and raise issues if anything seems broken / is unclear etc 