It appears that XMLTYPE is still not working correctly in SQL Developer EA4 Version 22.214.171.124 Build MAIN-13.30.
The following produces an XMLTYPE result, but it is not viewable:
This works correctly in SQL Developer 3.
Note that doing a .getClobVal() on that result does give the text string of the XML, so it is a view problem in EA3 that doesnt show the raw XMLTYPE.
yeah, it's a DB bug (16881111), which is addressed in 126.96.36.199
As a workaround you can execute this as as script (F5), or use getclobval() in your statement