P: End-to-end encryption for my photos?

I suspect the lack of E2E encryption is a design decision based on the desired functionality of the Lightroom ecosystem. Lightroom's cloud features were originally intended to facilitate sharing and to provide a backup solution for the average consumer who doesn't know how to manage backups on their own.

There have been countless beginner to intermediate users right here in the forum who have been saved by the Adobe team being able to restore seemingly lost photos. And many people (myself included) use the sharing function to collaborate and share photos with less technical people. 

None of this would be possible with true E2E encryption, which puts the burden on the user to manage their data and the keys. If you're sophisticated enough to understand what E2E is, and you have a need for it, you're better off having your own backup solution and managing it in a zero-trust configuration. Lightroom is not that, doesn't try to be that, and personally I doubt it would ever be. 

Note that I don't work for Adobe, don't have any inside information about future developments, and this is my own opinion. 

I suspect your question can only be answered by Adobe staff. However, it's worth noting that a similar question asked in 2020 can be seen at https://community.adobe.com/t5/lightroom-ecosystem-cloud-based-discussions/usage-of-lr-with-own-cloud-storage-or-automatic-end-to-end-encryption/m-p/11716608

The question received no reponse from Adobe or other Lightroom users.