If you're hosting the service, there's no need for data to be encrypted client-side. Unless, of course, you were intending on running the service on a public cloud which you didn't control, but that's something I don't think many privacy conscious folk would do.
There's plenty of open source, self-hosted alternatives to Google Photos.
Most likely, QoS would be better from ente's hosting and I would be inclined to take advantage of that. An open source server can be audited and offer an off-ramp should their service no longer suit me.
Then again, the economics of enabling self-hosted infrastructure are probably less exciting compared to locking users in to marked-up, white-labeled infrastructure.
For web apps, the situation is even more difficult, but there is a technique called Secure Bookmarks which allows you to confirm that a specific bundle of JavaScript is running (at the expense of some usability):
Of course it's still possible that an update could be sent to everyone which contains some code that only runs when a certain username is entered, so users would need to avoid updating the app until an audit by a trusted third party had approved it.