In RepU, open your widget and click Copy next to the embed snippet.
In the Duda editor, click the Developer Mode icon in the top bar, then Site HTML / CSS, and open body-end.html. Paste your code on the last line, click Save, then click Done.
Publish your changes, then open your live site to see your Google reviews.
Check your live site in a private window, not the Duda editor or preview. A domain-locked widget only shows on your own domain.
Built by an agency? If you cannot see Developer Mode, ask them to add your code, then check again.