Maybe this isn't the right place to put this but it seems like the concurrency implementation was only partially implemented. Perhaps this is documented elsewhere that some of the functionality is to be implemented later on in the process, but as an example, swift-corelibs-foundation does not provide async/await APIs, which means it cannot be used on URLSession methods outside of Apple platforms.
I had a thread here referencing this How to use async/await w/ docker.
Again, maybe this is something to be expected, but given the push for Swift adoption outside of Apple platforms, I would have thought that this functionality would be able to be experimented with on nightly 5.5 builds/docker images.