Hi @asherber - on the extensions page, it says that dict_xsyn is a superuser-only extension and not generally available to install. I don’t know why, but this might be because it accesses shared files on disk, the size of which is not tracked (hence potentially violating the space limit), or which at least require access that we don’t have to use.
Meanwhile, xml2 is not listed there at all, despite being visible in
SELECT * FROM pg_available_extensions;
I suspect this is because the xml2 extension is deprecated. You might want to look into moving to the XML type and functions, including XPath 1.0.