By default, WebCatalog uses the same proxy settings as your operating system. You can configure proxy in your system settings:
Ubuntu (Linux): https://help.ubuntu.com/stable/ubuntu-help/net-proxy.html.en
You can also set proxy settings in the app/space settings (Settings > System > Proxy). See: https://docs.webcatalog.io/en/articles/8431198-how-to-change-app-settings
Additionally, you can also set proxy settings by subspace. Learn more about subspace settings: https://docs.webcatalog.io/en/articles/8433052-how-to-change-subspace-settings