Yes, it is possible as indicated in the Electron forge makers documentation:

• Squirrel.windows You can only build the Squirrel.Windows target on a Windows machine or on a macOS /Linux machine with mono and wine installed
• Deb (linux) You can only build the deb target on Linux or macOS machines with the fakeroot and dpkg packages installed.

  makers: [
    {
      name: '@electron-forge/maker-dmg',
      config: {
        icon: `${iconPath}.icns`,
      },
    },
    {
      name: '@electron-forge/maker-squirrel',
      config: {
        authors: 'YOU',
        iconUrl: 'https://your_site/favicon.ico',
        exe: `${BUILD_NAME}.exe`,
        name: BUILD_NAME,
      },
    },
    {
      name: '@electron-forge/maker-deb',
      config: {
        options: {
          bin: BUILD_NAME,
          maintainer: 'YOU',
          homepage: 'https://you home page',
        },
      },
    },
  ],

Personally, I run the build in a Gitlab CI.

This allows the Windows shared runners use rather than a docker (linux) image with Mono because that was causing me some problems on Windows execution.

For the mac part I register a gitlab runner on my machine before launching the publish phase on gitlab.

I think you can achieve the same result very quickly with Travis who already has mac and windows runners available.

I hope I helped you. Good luck