It's definitely possible to be a left-wing nationalist

I mean it's definitely possible to call yourself that, but I'd argue no, it's not possible to actually be that.

Famously, Mao Zedong was neither left-wing, nor a nationalist, right?

Then you have never studied communist eastern countries and their nationalistic policies.

https://socialhistoryportal.org/news/articles/110357

No-one defines what they mean by "nationalist" so it could apply to a rock.

That takes a form more like "let's make our country the best country ever" than "let's kick out everyone with a different skin color"