I was having the same problem in 26.4. I didn't try 26.5 beta 1, but I did try the newer 26.5 beta 2 and the same problem occurs. It would be interesting to hear OP's experience with beta 2!

FWIW, I'm seeing something similar to the original problem, occurring when I try to run code inside the new #Playground structure in Xcode 26 (beta 7). Any attempt to execute an URLRequest ends in "A server with the specified hostname could not be found." I've tried a number of things mentioned in this discussion, such as using "URLSessionConfiguration.ephemeral" and setting "tlsMaximumSupportedProtocolVersion = .TLSv12". Is this simply unsupported behavior inside of a #Playground, or am I missing something?