In Safari AppExtensions we have this API made available
optional func contentBlocker(withIdentifier contentBlockerIdentifier: String, blockedResourcesWith urls: [URL], on page: SFSafariPage)
Is there something made available to WebExtension given WebRequest blocking isn't available in Safari.
Safari Web Extensions have the DeclarativeNetRequest API, where you can specify rules in that format.
Check out https://developer.apple.com/documentation/safariservices/safari_web_extensions/blocking_content_with_your_safari_web_extension?language=objc for some information on that.
New in Safari 15.4, we added support for the getMatchedRules API. You can see some documentation about that at:
https://developer.chrome.com/docs/extensions/reference/declarativeNetRequest/#method-getMatchedRules
Hope this helps!