We no longer recommend using the S3 mirror for cocoapods as it has not been updated in many months. Since Cocoapods 1.8, it is better to use the CDN method of retrieving pods as it has better reliability and is generally faster: https://circleci.com/docs/2.0/testing-ios/#optimizing-cocoapods
Cocoapods 1.9 isn’t working very well with Xcode 12 at the moment, so in the next image (12 beta 4) we will be shipping Cocoapods 1.10 beta which brings Xcode 12 support. Keep a check on the announcements section as it shouldn’t be long before this is rolled out!