Reference (microsoft/vscode#31168)
find /usr/share/ -name "product.json"
# cd into vscodum directory
cd /usr/share/vscodium-bin/resources/app
nano product.json
# search for "extensionsGallery" and replace it with
"extensionsGallery": {
"serviceUrl": "https://marketplace.visualstudio.com/_apis/public/gallery",
"cacheUrl": "https://vscode.blob.core.windows.net/gallery/index",
"itemUrl": "https://marketplace.visualstudio.com/items"
}, # Don't forget the comma!