There seems to be one place that still uses a LoadBalancer directly when it shouldn't:

	private function getLocalConnectionManager() {
		if ( $this->localConnectionManager === null ) {
			$this->localConnectionManager = new SessionConsistentConnectionManager(
				MediaWikiServices::getInstance()->getDBLoadBalancer()
			);
		}

		return $this->localConnectionManager;
	}

Maybe a ClientDomainDb should be injected in the constructor?

(Also, my IDE complained that the field $entityNamespaceLookup is unused in this class. Probably worth double-checking and cleaning up while one is touch it anyway.)