GET https://graph.microsoft.com/v1.0/applications?$filter=tags/any(c:c eq 'Request-number') worked fine for me.
Used the below Java code snippet to apply the filter on tags.
ApplicationCollectionPage appPage = getGraphApiClient().applications().buildRequest()
.select("id,appId,identifierUris,appRoles,signInAudience")
.filter("tags/any(c:c eq 'application_type:resource_server')").get();