Since Apple and major retailers stopped selling the iPhone 6 years ago, you will need to look at used or refurbished marketplaces:
Are you planning to use this as a or just for a specific purpose like a music player? Use iPhone without Carrier - Apple Support Community can you buy an iphone 6 without a plan
Ensure the listing explicitly says "Unlocked." A "locked" phone is tied to a specific carrier (like AT&T or Verizon) and won't work with other SIM cards unless the previous owner paid it off and unlocked it. Since Apple and major retailers stopped selling the
Before you buy, keep in mind that the iPhone 6 is very limited today: It will connect to Wi-Fi for apps, iMessage,
You can use the iPhone 6 like an iPod Touch. It will connect to Wi-Fi for apps, iMessage, and FaceTime without any SIM card installed.
Many modern apps (like YouTube, banking apps, and newer games) require iOS 15 or higher. The iPhone 6 is stuck on iOS 12 , meaning many apps will not download or function.