You can download any website as an HTML file (without the site's assets) using cURL in the command line, using the -L flag to follow any existing redirects.
curl -L https://nono.ma --output nono-ma.html
The manual alternative is to right-click on a website on your browser of choice (say, Google Chrome or Firefox), select Save As.., and save the site as HTML with some of its assets in a subfolder.
Afterwards, you can convert the downloaded HTML page into a Markdown document with pandoc.