Surfing the federated universe!
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.
To my understanding, they are still supporting plugins, it’s just they won’t provide the list of apps, you should be able to add your own repository of plugins to download, in fact, there are some going around.