“an all-in-one subscription that bundled together your choice of Pixel phone, Preferred Care protection, Google One cloud storage, YouTube Premium, Google Play Pass, and (optionally) Fi Wireless service.”
From https://9to5google.com/2023/08/29/google-pixel-pass-ends/
Started at $55. Shame it never launched in the UK (or elsewhere)
Don’t even need an app. I got an eSIM via a QR code (which went to a website where the eSIM was downloaded). This was on a Pixel 6. I guess the process may be different on other phones.