UPDATE: problem persists even after updating OS to 12.2, updating Chrome to 97.0.4692.99, and updating all browsers' permissions as noted above, and doing a full system restart.
Chrome, will NOT download, upload, or print to PDF
Edge, will NOT download, upload, or print to PDF*
Safari, WILL download and upload, but will NOT print to PDF
Firefox, WILL upload and download, will NOT print to PDF
Preview, WILL print to PDF.
As before, the features above that ARE working, I would expect to eventually begin not working, based on prior experience.
Clicking on the Download button on sites also does nothing. The buttons don't even highlight or anything to show they've been clicked. However, it seems there IS an upload/download process that has been initially triggered, but it goes nowhere. Because if I click on download buttons in Edge or Chrome, they do nothing at all. But if I then close the app, I get a warning telling me that a download is still in progress. I confirmed that there are not any partially completed or in-progress downloads in my Downloads folder. But it knows the process was attempted. This seems like a system-level problem. This is also identical to how the Save to PDF error fails: clicking on the button to do so shows absolutely NO visible response.