Sorry. I have no experience with other xmpp servers, especially not aware about xep support. You can check out ejabberd, prosody, tigase. Ask in their forums. I’ve heard those servers are advanced enough, but maybe don’t have such an easy administration panel as Openfire.
Support for XEP-0198 Stream Management has been added to Openfire and is available now in the latest pre-release builds. Note that the stream resumption capabilities are not yet supported, but the ack request/answer scenarios are fully implemented. The new WebSocket plugin also supports the XEP-0198 acking features when deployed using the latest nightly Openfire builds.
We expect the new stream management features will be included in the next incremental release of Openfire (3.11.x).
Check the link “latest pre-release builds” in Tom’s message. It points to nightly builds download page. Nightly builds should include features described by Tom.