How can I fix my iPhone 8 charging issue with multiple chargers?

Either you have an issue with the charging port or the battery likely needed to replaced some time ago. iPhone 8 was released in 2017, 8 years ago. If the battery in your phone is the original battery, it's likely is long overdue for a new battery. Whether it would be worth investing any money in an 8 year old iPhone, which can never run any iOS version higher than iOS 16.x.x is up to you. I would not invest in having the phone fixed and would instead apply what the cost of repair would be towards a new iPhone. schedule an appointment at your Apple Store Genius Bar and apple can explain your options --> Genius Bar Reservation and Apple Support Options - Apple

Search for accessories that have completed MFi certification. Once an accessory has completed MFi certification requirements and is reported to Apple as sold/distributed, it will be searchable in our public database of authorized Lightning, headset, charging, iAP-enabled, and Find My network-enabled accessories.

Learn how to identify counterfeit or uncertified Lightning-based accessories.

Follow these steps:

• Remove any debris from the charging port on the bottom of your device.
• Restart your iPhone or iPod touch.
• Try a different USB cable or charger.
• Make sure you have the latest version of iOS.

If your iPhone or iPod touch won't charge - Apple Support (IN)