Could you check if Edge gives any detail as to the reason for the security flags? I don't seem to be seeing this behaviour on my side, and I wonder if it may be smartscreen's reputation system doing its thing again. Often when we post a download link, it takes a few days before the reputation increases and smartscreen accepts it (regardless of signing apparently).
We've been using the same automatic download S3 links for about a decade or so now. The only recent change was to the static links on the download landing page (the ones you need to click on if the download doesn't start automatically)