[2020] Windows 10 is not letting me install Valorant

This could be related to some installer corruption we have been seeing on and off over the past week or so. If you redownload the installer from the website and try again does it work? What region are you playing from (BR, KR, LATAM, NA, EU)?

I don't believe this has to do with UAC. I believe this warning is typically related to executable signing.

This error does not necessarily imply software is malware, I believe it is related to executable signing. You can run into this warning when a company renews their code signing certificate for example. In our case I don't believe we have renewed the certificate recently (if I remember correctly I renewed it at the beginning of this year) so my theory is that it is potentially related to some corruption (for example some parts of the executable being missing) that occurs when you download the installer from one of the companies we use for CDN purposes. The corruption could potentially cause the signature to not look right and this warning to pop up? Also the publisher says unknown and not Riot Games like I would expect which also reinforces that theory.

Another thing that may further reinforce that theory is that the thread starter said that they are never able to get past the error which to me means that they clicked run away and due to the corruption it crashes. If this is caused by corruption, we unfortunately haven't gotten to the bottom of the issue yet and are still investigating why it happens and how to fix it. It doesn't seem to be happening as often recently though.