you can use the node based tiddlywiki and it saves the tiddlers in seperate text files. with the markdown plugin it saves to markdown. With obsidian you can use the markdown as well, or with kiln you can export to gemini or the small web

will it work like external storage, or like backup/export on save ?

It autosaves to the filesystem whenever you make edits. Until you hit save, though, it saves them to a separate Draft file.

That's why I use it with git. Not only do I get the ability to revert a catastrophic fuckup, I also get the ability to securely sync across all of my computers.

The only thing missing to make it perfect would be a mobile client, but that's not huge deal for how I use it.

The thing I don't like though is that, because it's all in a single giant html file, it is prone to getting huge. Mine is pretty big, and every time I open it (in Firefox or TiddlyDesktop) there's a noticeable delay.

I'll have to look into breaking the monolith up into smaller files to avoid that.

There is a mobile client that works excellently called Quine 2. Ive been using it for a couple of years with a mobile accessed Tiddlywiki personal wiki and it works pretty good. I keep the file on iCloud and can open it from desktop and mobile.

Thanks for the suggestion, that app works great!

I managed to set it up with my repo using an app called Working Copy, so now I have the full workflow going on all my devices

Well, in a sense it is plaintext as your data are kept in simple divs within the html file - just open it in notepad and all your data is there!