Reproduced this issue also on https://www.thinkbroadband.com/download - tested on Windows 7 and Mac OS X 10.15 using the latest Nightly 80.0a1 - the Save As dialog is not opened when trying to download any file.
Bug 1654139 Comment 4 Edit History
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Reproduced this issue also on https://www.thinkbroadband.com/download - tested on Windows 7 and Mac OS X 10.15 using the latest Nightly 80.0a1 - the Opening dialog is not displayed when trying to download any file.