Apple: ‘iCloud Private Relay Overview’ (PDF):

New whitepaper from Apple with a lot of details about how iCloud Private Relay works. Still doesn’t list Apple’s CDN partners for the second relay hop, but that’s obviously some sort of strategic decision on Apple’s part. As the paper makes clear, you don’t need any particular trust in those CDN partners, because they never receive anything that could identify you, or locate you any more precisely than an 800 km² region.

iCloud Private Relay is still officially in beta, but it’s been so reliable for me that I had to check just now that I’ve got it enabled on all my eligible devices.

Source: Daring Fireball