Joplin is a free open-source application for handling your note taking and to-do lists.  The developer does not charge for using the application but does accept donations.  The application helps you write and organize your notes and synchronize them between your devices.  In fact, the notes are searchable, can be copied, tagged, and modified from within the application or using your own text editor.  Joplin uses the Markdown format the same as Notion.  Joplin can be downloaded on a desktop, mobile and terminal application.