The Smart Screen issue hasn't been solved on Unity 5.5

If I download my game built with Unity 5.5.0b1 form itch.io and then try to run it, I get the following message:

It all started with Unity 5.3.6, Unity 5.4 didn’t solve it, and is still present on 5.5

It’s not a bug. It’s a windows feature. It does that when you download unknown and unsigned executables from the web and try to launch them. Here’s a discussion about it with possible solutions:

If this is not a bug, as you say, then explain why I don’t have this problem if I build my game with Unity 5.3.5.f1.

Read the thread I linked for details on how SmartScreen works. It’s not something you can affect by changing code in your executable.

I think you are wrong, any game built with Unity 5.3.5f1 or previos can completely skip Smart Screen, try it yourself please. Build what ever project you like with Unity 5.3.5f1, generate a zip file, upload it to any web server you have available, download it, unzip it and run the exe file. no Smart Screen window appears!… then build it with Unity 5.3.6 or latter, do the same and you will see the Smart Screen window!

Please read my post on the thread you linked.