Jetpack’s Flickr widget embed your Flickr photostream to any widget and block area on your site.
To add the widget, go to Appearance → Widgets and add the Flickr widget into your chosen widget area.
You can add it on posts and pages as well. Just look for Flickr on your Block editor.
To find your Flickr URL, go to the Flickr photostream and select the URL at the address bar.
Copy the URL to the field and click on the Embed button. It will load your gallery photostream to your widget/block area.