Note-taking apps differ most in how they store your notes. Some keep plain Markdown files in a folder you control, others use a database or a proprietary sync service. That choice decides how easy it is to back up, search with other tools, or move to a different app later.
Logseq and Joplin are open source and keep notes on your device, with Logseq built around outlines and linked notes. AppFlowy and AFFiNE are open source workspace apps in the style of Notion, and FSNotes is a native Mac app that works with plain text and Markdown files. Check whether sync is built in, uses your own cloud folder, or costs extra.