Actual in 2020 replacement to Evernote app

I'm looking for (preferably open-source) solution, replacing Evernote application and service. Main reasons of the move are terrible usability, bugs and privacy concerns. My preferences are simple.

- GUI: Markdown is preferred but not required format (I understand it's not an option for non-tech people, which would cut the possible application audience), hierarchical structure of notebooks and notes, tags.

- Sync options: using existing cloud service (preferred) or self-hosted solution. Reasonable privacy and security options.

- Stable release, not unusable beta.

- Possibility to import existing notes from Evernote (enex format)

- Applications for Mac, Windows, Android and iOS