with expo sdk52, "react-native-purchases": "^8.5.0", pod install --repo-update
I had this error message
[!] CDN: trunk URL couldn't be downloaded: https://cdn.cocoapods.org/Specs/9/a/d/PurchasesHybridCommon/13.15.0/PurchasesHybridCommon.podspec.json Response: Error in the HTTP2 framing layer
fixed it by updating cocoapods :
CocoaPods 1.16.1 is available.
`sudo gem install cocoapods`
Et voilà ;)