I would not want to say that it is because of coronavirus ;-), butI think there is a compression problem in the files proposed recently in 3.1.0 MAC (console AND off line) on the software section.
They don't normally decompress to make a .fw or.dmg
It seems working, with Windows tools, but not as usual, with MacOs tools.
I downloaded with Mac Safari and have had no issues installing either files.
Yes, you are right, it is probably because of Chrome that there was a problem, yet I had attempted the download twice. Since ETC modified its site, I had problems with Safari. There for example, I can no longer respond without an error message. I have to go through Chrome. But for the download it seems to work.Thanks