OpenNote is built to be an open web-based alternative to EverNote but is still in development: https://github.com/FoxUSA/OpenNote
Maybe the Zim desktop wiki is an alternative to you: http://zim-wiki.org/ All information are saved in plain text files including attachments and can simply be syncronized between different devices (i.e. by dropbox). There is also a firefox plugin to copy selected text of a web page or bookmarks into Zim.
I just looked at their privacy policy and I agree - it's terrible. I recently started the move toward Linux and after 10+ years of using the wonderful Keynote program, I'm also looking for a Linux alternative.
Even 10 years ago, I knew I would eventually have to deal with this cross-platform barrier with Keynote. I might take a look at OpenNote (found it just now from the /r/selfhosted link mdaniel supplied).