Darkside (DRKSIDE) was written on Matt’s Vehicle registration plate in Something Human Music Video.

On the 26th of August 2018, Muse posted four pictures from the music video on social media. Two days later, on the 28th, Matthew Bellamy posted a video of the guitar solo on Instagram, and it was later released on the band’s social media accounts.

As Lance Drake -Director of the Music Video- stated:

The Dark Side is about fear, paranoia, mental illness, and depression. Sometimes the dream is a nightmare and grand visions are in fact crumbling illusions. Don’t get caught up in the upside-down, keep driving!

In response to one of the fan’s tweets, Matt has stated the song contains angry lyrics and has the common Muse themes of frustration and loneliness. He further explained in an interview with Radio X, that the song and Algorithm deal with the struggle to get away from a dystopian world and the anxieties about technology, trying to escape your anxieties or from some kind of matrix.

One way to interpret the lyrics and the music video is just as the director said. It is about overcoming your fears and problems and keeping driving no matter what happens.
However, this song has another annotation which connects it to the rest of the album as a part of the storyline. It is described below:
After the protagonist realizes that he is just living inside a simulation and he is not actually real, he tries to break out to set himself free.
As he disappears at the end of Something Human, he appears to be in a secure area which could be the core of the simulation.
As he moves toward the main core -the mind- the simulation itself tries to stop him.

After he escapes, it seems there are other simulations like a multilayer virtual world.