I can't say we can count on this working across all machines today.
As to the DNS, did you try that suggestion?
I find some want to avoid this one and may use "other things work OK" as the reason to not try it. In short, you listed very different machines so one machine is not like the other, something isn't quite the same (yes, Sesame Street reference.)
Recently, I've been receiving this message frequently. WHen clicking on a link, this message will appear. When it does, it's not just that site, but usually others that were open. After a few minutes they start again. Some days, it doesn't happen at all. And others, like today it's happened about 10 times already. Thinking it had to do with my internet, I had a long conversation with Spectrum, and they even sent out a tech guy who said it wasn't their fault. Also, had a long conversation with Apple tech and they couldn't solve it. So, doing a little searching, I found that it happens frequently to people. The suggestions were a bit scary for me to try without more information. So, what was said most often is that it has to do with the DNS configuration. I have an iMac, Chrome and gMail and it's only on the iMac that there is any problem. My iPhone and iMac work just fine.. Help greatly appreciated! Peggy