After doubleclicking the new mp3tagv290setup.exe on my Win10 Pro, I get a warning about "unrecognized App" which "might put your PC at risk". This warning appears only once.
Something like this
or
It's not a big problem, just to let you know.
(I know, how I can adjust my SmartScreen settings to disable this warning)
I've did some further research and learned that SmartScreen seems to assign reputation to an application after it is installed on many systems from different IPs. This reputation then also spills over to the code-signing certificate that is used to sign the application.
This explains, why releases of Mp3tag signed with my previous certificate (which was in use for 3 years) had immediate reputation and didn't show the Windows Defender SmartScreen warning at all.
I've now uploaded a file using my new certificate to the developer dashboard at Microsoft, hoping that this will speed up the process of earning new reputation for SmartScreen.