the only thing I could think of doing with minimal effort- which I might add would look pretty obvious and awful -is a lazy trick from audio editing. basically reverse it along the axis you’re aligning it on every second tile, like this:
That’s it tiled 2x2 with the respective horizontal and vertical transforms applied. As you can see, it looks pretty godawful. It works slightly better for less feature-rich textures, but at that point there are better filters you can use.
here’s that texture tiled as 2x2. it looks more like the background to a psychedelic music video than a texture by this point:
one would imagine you could compensate for the sheer awfulness of this texture with more creative use of UVs, but then again you could also go out and get lucky with a celebrity.
So unless you want to spend time in a doctoring program removing the defining features and adjusting the texture to be more tile-friendly, you’re pretty much stuck with a lazy result or a non tilable texture.