BAD signature when trying to verify SHA256SUMS for Bionic Beaver ISO
Solution 1:
ostensibly_work over at reddit solved the problem.
I did not realize that right clicking and selecting "Save Link as" downloads the file directly. With that, the gpg signature checks out.
Thanks for the help everyone!
Solution 2:
You mention your worry for having passed the downloaded text of SHA256SUMS through Windows' notepad, and you're absolutely right to be worried about it.
While this doesn't appear to have altered any of the text, it does alter it, by changing the end-of-line marker, from the default Unix/Linux style of just LF (\n) to CR+LF (\r\n), the default end-of-line in DOS/Windows style.
I'd bet that, if you try it again, this time downloading the SHA256SUMS file directly to disk, instead of copying and pasting it into notepad, the signature would then match. Doing the same to SHA256SUMS.gpg wouldn't hurt, either, but is probably not required, in order for the signature to check out ok.
To do so, you'd just need to right-click the link to the files, and choose to save them to disk. Another way of doing it would be to, after opening the files in the browser window, choosing the Save command in your browser.