This blog is updated daily.
A general description is here.
All builds have support for 'https:' URLs in 'download.file()', 'url()' and code making use of them.
Unfortunately that cannot guarantee that any particular 'https:' URL can be accessed. For example, server and client have to negotiate a cryptographic protocol (TLS/SSL, ...) and the server's identity has to be verifiable _via_ the available certificates.
The undocumented switching of methods for 'url()' on 'https:' and 'ftps:' URLs is confined to 'method = "default"' (and documented).
'file()' gets an explicit 'method' argument instead of implicitly using 'getOption("url.method", "default")'.
(Windows only) Function 'setInternet2()' has no effect and will be removed in due course. The choice between methods '"internal"' and '"wininet"' is now made by the 'method' arguments of 'url()' and 'download.file()' and their defaults can be set _via_ options. The out-of-the-box default remains '"wininet"' (as it has been since R 3.2.2).