I've been looking high and low for an Evernote alternative for Linux. I know I can use Everpad or Evernote in WINE but they don't work natively.
Any note-taking app would be fine as long as it can sync my android and my linux.
You can use a wiki like Zim - a Desktop Wiki and save its files to a Dropbox folder. For Android you can use WikiMind note to work with the Zim Wiki. I'm sure there are other apps that can work with Zim's files since they're just text with wiki markup.
Other options for Android if the $3 price for WikiMind is too steep.
There is an Evernote add-on for Thunderbird.
Google keep seems to be quite good:
Dropsync app is needed to synchronize the dropbox zimwiki notebook folder with the wikimind (lite or full) folder
TagSpaces is a document managing application that also support note writing, and it can run on both Linux and Android. It does not provide a synchronization feature natively, but you can combine it with DropBox, OwnCloud or SpiderOak to sync between your devices.