When releasing my app in AppStore I’ve notices that it wants screenshots for a lot of different screen sizes before I can send the app for review. I’m using AppFlow because I don’t have Mac hardware - And without this hardware and access to Xcode, how can I get screenshots for those devices?
Run the app in a browser, open responsive mode and choose which sizes you need. But anyways: I would recommend you to buy an iPhone, as you should test your apps on a real device before going to production
I use macincloud.com to get access to Xcode allowing me to do app builds, test my app in an emulator, and do screenshots. browserstack.com is also a good option to just test an app build and get screenshots. Obviously, nothing beats real hardware but I can’t justify the cost yet for that. Gotta love Apple’s closed ecosystem…sigh…
Einfach’s answer is great if you don’t have a device. Otherwise, search for screenshot generator to find a variety of free and paid tools that can help.