https://bugs.winehq.org/show_bug.cgi?id=38409
--- Comment #11 from Nikolay Sivov bunglehead@gmail.com --- Looks like it's back in a form of additional program/plugin - https://github.com/davidedmundson/xembed-sni-proxy. Some developer notes are also here http://blog.davidedmundson.co.uk/blog/xembed_back (interesting blog engine that doesn't display posting timestamp). As far as I can tell the idea is to merge this directly into Plasma 5.5 so users don't have to bother installing this bridge separately. And of course I have no idea how well it works for Wine or if it works at all at the moment.