Currently there is no way to get a list resembling this:
"localRdfNamespaces": {
"": "http://default.web.mw.localhost:8080/entity/",
"data": "http://default.web.mw.localhost:8080/mediawiki/index.php?title=Special:EntityData/",
"s": "http://default.web.mw.localhost:8080/entity/statement/",
"ref": "http://default.web.mw.localhost:8080/reference/",
"v": "http://default.web.mw.localhost:8080/value/",
"t": "http://default.web.mw.localhost:8080/prop/direct/",
"tn": "http://default.web.mw.localhost:8080/prop/direct-normalized/",
"p": "http://default.web.mw.localhost:8080/prop/",
"ps": "http://default.web.mw.localhost:8080/prop/statement/",
"psv": "http://default.web.mw.localhost:8080/prop/statement/value/",
"psn": "http://default.web.mw.localhost:8080/prop/statement/value-normalized/",
"pq": "http://default.web.mw.localhost:8080/prop/qualifier/",
"pqv": "http://default.web.mw.localhost:8080/prop/qualifier/value/",
"pqn": "http://default.web.mw.localhost:8080/prop/qualifier/value-normalized/",
"pr": "http://default.web.mw.localhost:8080/prop/reference/",
"prv": "http://default.web.mw.localhost:8080/prop/reference/value/",
"prn": "http://default.web.mw.localhost:8080/prop/reference/value-normalized/",
"no": "http://default.web.mw.localhost:8080/prop/novalue/"
},from WikibaseRepo. There should be somewhat to get this.
See: https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Wikibase/+/589046 for an example we tried in the prototype