Thomas, as per your email: I attempted the original download within Firefox browser. I got the Opening yEd-3.13_64-bit_setup.sh as above and chose save to file as illustrated. I've deleted that file from the Downloads folder using GUI. Now I'm attempting to download once again using chromium-browser for Linux Mint OS--the Google Chrome replacement for Linux.
Descargas, I'm working on your work around suggestion, too. However, I'm using a public Internet location that has a slow connection, and the download keeps failing. I will keep trying from here or elsewhere and report back if it works.
Thank you all for your help. I'm really excited about my new Linux experience and need this tool (and others) to work for me in order to escape the Windows/Microsoft clutches.