The default system font stack in MacOS uses .SF NS, but that is not a selectable font in Figma. SF Pro Text and SF Pro Display are similar, yet different fonts. Is there a way to use the default system font stack in Figma?
Unfortunately, there isn’t a way to do what you’re thinking, in a way that would be easily manageable in Figma. Your best bet is to use a font (e.g. Inter) as a proxy for a system font: “Hey devs, Inter == System…”
In theory, if you could find some way to download/activate those system fonts, you could reference them in your design. But this might cause nasty conflicts.
There might even be some third-party apps not officially endorsed by Figma that help in this regard, e.g. a Figma editor app that has its own font manager.