Chromium reads policy JSON files stored in specific system directories. Open your Linux terminal and create the required managed policy directory structure by running:
sudo mkdir -p /etc/chromium/policies/managed/
Generate a JSON configuration file inside that directory containing the target URL policy strings. You can use nano or any text editor to create a file named custom_new_tab.json:
sudo vi /etc/chromium/policies/managed/custom_new_tab.json
Paste the exact JSON structure below into the file.
Replace https://example.com with the actual website or local HTML file path you want to open:
{
"NewTabPageLocation": "https://example.com"
}