Even Google also gives actual E2EE by default for Android backups. Same with Samsung. Others have mentioned that Proton and others do this for services that Apple won't.
https://developer.android.com/privacy-and-security/risks/bac...
https://developer.android.com/privacy-and-security/risks/bac...
Google Photos is meant for sharing, where E2EE makes little sense. You can search your photos from any device.
If you really want to give up that convenience for E2EE, you might as well do it right and use Proton or Ente, which have E2EE for all photos, unlike iCloud, which isn't for shared albums or photos shared to anyone with the link. Unlike iOS, Android lets these apps have access to all the same device APIs as Google Photos, meaning they're as seamlessly integrated as possible. Apple iCloud uses iOS APIs not available to third parties, locking you in to using either a gimpy service or a gimpy app.
[1]: https://ente.io/ml