You solved it for users using JCache, giving the possibility to define missing_cache_strategy "create",

but the issue creator clearly stated that he is using ehcache directly not jcache.

No, we (at least tried) to solve it for both: https://github.com/hibernate/hibernate-orm/commit/c52ff4d06c95302fbf66b6c0dc2ac79f81819b81#diff-59b8d24e6179e8fa85722b3e4641de0cR108

The EhcacheRegionFactory class is still affect by this issue as it still does not allow on-the-fly creation (see line 106).

Did you try the latest release, 5.3.2.Final, released yesterday? Or are you saying that based on an older version of the code?

Overmore there it says "On-the-fly creation of JCache Cache objects is not supported .."

instead of "On-the-fly creation of EHCache Cache objects is not supported .."

This was fixed too: https://github.com/hibernate/hibernate-orm/commit/c52ff4d06c95302fbf66b6c0dc2ac79f81819b81#diff-59b8d24e6179e8fa85722b3e4641de0cR117