Hi Joe,
As others have mentioned, I download all of my Medium articles as a ZIP file once a year. It's not a perfect solution, but it works.
When it comes to Freelance writing, I save the links on a PDF on my laptop (in the cloud). So, even if the actual link goes offline for whatever reason, I can use the internet archive to prove I published somewhere.
That's what works for me. Hope you have a wonderful day, Joe! :)