I’m totally in favor with your post, but not everyone is willing to self-host or is capable of doing it. So I recommendation would be and one that I’m currently using, is when uploading a file to these cloud services encrypt your files. I’m using #cryptomator, but I’m sure there are other alternatives, like #rclone. There is also #veracrypt, but to my understanding, is not great for cloud sync.

Cryptomator official website
Quick youtube video in how to use cryptomator (3:51)

Cryptomator is open source and free, but only on desktop. To use the mobile version, you will have to pay. Here is a list of alternatives to cryptomator, if you are familiar with one, please share your knowledge.

When I found out about this app, I was blown away about how cool the concept is. Sadly it was already dead, at that moment it made me wonder why other services weren’t build like that. I don’t think it will be easy to create a service like that and probably have too many downsides I’m not aware.