1.- sudo apt install fonts-firacode

2.-actualiza cache con:
sudo fc-cache -fv

luego verifica la instalacion con: 
fc-list | grep "Fira"

3.- pega el siguiente json en el archivo json de configuracion de vscode
{
    "editor.fontFamily": "Fira Code",
    "editor.fontLigatures": true,
    "window.zoomLevel": 1,
    "git.openRepositoryInParentFolders": "never",
    "security.workspace.trust.untrustedFiles": "open",
    "workbench.iconTheme": "material-icon-theme",
    "prettier.bracketSameLine": true,
    "editor.wordWrap": "on",
    "screencastMode.fontSize":20,
    "editor.tabSize": 2,
    "screencastMode.verticalOffset": 3,
    "settingsSync.ignoredExtensions": [
        "ms-ceintl.vscode-language-pack-es"
    ],
    "application.shellEnvironmentResolutionTimeout": 25,
    "workbench.colorTheme": "Night Owl",
    "launch": {
        "configurations": [
            
 
        ]
    }
}