These types of speculative theories purporting that they can solve dark matter/dark energy appear many times per year. I usually don’t really pay attention to them until they are more mature.
For this one, the dark matter/energy is replaced by a fluid with expulsive gravity permeating the universe. While the particulars of this fluid might be new, note that there were many previous speculative theories where dark matter/energy is assumed to be a fluid (or even a quantum fluid).
Here’s the paper, it is getting a lot of press.
The headline makes it sound like 95% of the cosmos is missing.