On Google Play you’ve plenty of good working apps like Memento, MobiDB etc. But sharing information with Windows and Linux you need a cloud account. Which i don’t like, because the data should be in my (encrypted) cloud.
One alternative is Binders from Generism, which works with one file. You can relate tables to each other. And there’s a Java-client to work on Linux.
Are there other apps where you can define your own fields and relate tables (contacts and events) to each other?