Launch VS Code Quick Open (Ctrl+P), paste the following command, and press enter.
Don't run this in your terminal!
ext install vsx-theme.visualix
Direct installation in your console:
(basically replace code with codium if you're using the VSCodium fork)
code --install-extension vsx-theme.visualix
Manual installation using VSIX file:
If nothing works, try this. You may also need to change the version to match the one in the repository.
The following code will download and install the extension on Linux.