Previous 8.6.x versions doesn't support Windows 32bit.
I expect we will probably move lts-13 to ghc-8.6.5 once it is released...
I'll try to get a nightly build with 8.6.5 this weekend
Great! I see that this works already:
stack setup --resolver ghc-8.6.5
I think that was something that was fixed in stack itself
Support for augmenting stack setup to support new ghc versions is done via the stackage-content repo. (This update must occur prior to moving the nightly builds over to the new ghc, and indeed it has.)