Efficient Diary is not available for Linux but there are plenty of alternatives that runs on Linux with similar functionality. The best Linux alternative is Joplin. It's not free, so if you're looking for a free alternative, you could try Standard Notes or CherryTree. If that doesn't suit you, our users have ranked more than 100 alternatives to Efficient Diary and many of them are available for Linux so hopefully you can find a suitable replacement. Other interesting Linux alternatives to Efficient Diary are Zoho Notebook (Free Personal), Trilium Notes (Free, Open Source), Cryptee (Freemium, Open Source) and RedNotebook (Free, Open Source).
Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, can be copied, tagged and modified either from the applications directly or from your own text editor.
RedNotebook is a graphical diary and journal helping you keep track of notes and thoughts. It includes a calendar navigation, customizable templates, export functionality and word clouds. You can also format, tag and search your entries.
WizNote is a Note software, which is especially designed for Internet users and mobile Internet users. WizNote focuses more on notes of rapid collection, management, reading and sharing. WizNote is smaller, more stable, and more suitable for computers, phones and mobile devices.