This is Ubuntu 22.04, x86_64. Any download I make from either browser just isn't done, and silently. It just proceeds, does not show me any error message, and no file appears. When the selected folder is the default Downloads folder (I configured both browsers to ask), the download happens normally. Smells like a security thing, but there's no user feedback.
In Firefox, I tried setting browser.download.improvements_to_download_panel in about:config to False. No effect.