Courtney Barnett and Kurt Vile don't necessarily makes the same music but they have overlapping fanbases who appreciate similar things. Mitski, too, but she's a lot "singer" than either.

I like some of their stuff but it's not usually my scene so I'm sure others will have better suggestions.

Also, I really like Gordi's cover of Avant Gardener

If you like this you might like Big Thief and Hurray for the Riff Raff, Kurt Vile is mentioned with her and they did make an album together. It's hard to find woman fronted groups or solo that are both as lyrical as her and rock as hard. Indie folk will be similarly lyrical but less noisy and fuzzy and indie rock groups will rock as hard or sound similar but Barnett's style of songwriting is less common in those genres.

I wish I had more. I even discussed this with my friends and we all drew to the same conclusion; we just don't know anyone like her.

There's a few artists like others have mentioned, but she's very unique in her style and writing.

Honestly, you're best of listening through her awesome discography and checking similar artists on whatever service you use online.

There's a lot of other great Australian female-led artists/bands similar to Courtney; Tired Lion, Camp Cope, Lyla Foy, The Jezabels, Thelma Plum... But at the same time, they're nothing at all like her, just some cross-over here and there.

Kurt Vile is definitely the closest for US. He's also the former guitarist of War On Drugs which have an amazing sound in the first albums he played in.

When I think Europe, there's really nothing too similar in "vibe" I have seen. Just a different post-2015 scene—which I personally loooove—but different vibe in their own cool way.

If you liked the brazen Australian accent just poetically overcoming their daft tone with strong words, I can recommend Wil Wagner - Laika, but be warned, you'll probably tear up if you're a dog or general animal lover. It's like the audio version of that Futurama episode. His writing is very similar. While his band, Smith Street Band, are very rock-centric, the writing is still raw, honest, and self-reflective of oneself. I'll post some of his stuff.