arswati wrote:
Is it possible to use third-party app stores on an iPhone without jailbreaking?
Only in the European Union.
About alternative app distribution in the European Union - Apple Support
How do these app stores function on non-jailbroken devices, and what makes them a viable option for users seeking alternative apps?.
"To reflect the Digital Markets Act's changes, users in the European Union are able to install alternative app marketplaces and install apps offered through alternative app marketplaces in iOS 17.4 or later, or iPadOS 18 or later. Users in the European Union can also install apps from a developer’s website in iOS 17.5 or later, or iPadOS 18 or later. The country or region of your Apple Account must be set to one of the countries or regions of the European Union, and you must physically be located in the European Union."
This appears to be the EU's description of the Digital Markets Act:
European Commission – The Digital Markets Act: ensuring fair and open digital markets
Apple is one of the designated "gatekeepers" and thus is forced to comply with the "gatekeeper obligations" as the cost of doing business in the European Union.