iPhones whose batteries have been replaced by third-party repair shops are now eligible for service at Genius Bars and Apple Authorized Service Providers (AASPs). The new guidelines are applicable worldwide and provide for both battery and component replacement but the guidelines are restricted only to third-party batteries. Apple will still deny service if any other component has been altered via non-Apple repairs.
https://www.notebookcheck.net/iPhones-with-third-party-batteries-are-now-eligible-for-authorized-Apple-repairs.413229.0.html