https://www.imyfone.com/iphone-space-saver/how-to-clear-reading-list-on-iphone/
Clear Reading List on Your iPhone/iPad (iOS 15 Supported)
The iPhone reading list allows you to save pages for reading later. For the sake of storage space and privacy you might want to clear them. Here are the ways.
on your iphoneipad ios 15reading listclearsupported