I'm not sure what you mean by snapshots, and it's not open source -- but if you haven't tried it yet, check out Obsidian. "Vaults" are self-contained, just mark

I'm not sure what you mean by snapshots, and it's not open source -- but if you haven't tried it yet, check out Obsidian. "Vaults" are self-contained, just markdown files in folders, with an extra folder for the Obsidian stuff, i.e. all settings and state and even the plugins. Plays great with SyncThing etc. And there are so many great community plugins, which is where the real magic of it is for me.