When you signed the app it is ready for uploading the app to stores. And when you are signing the app you are setting the developer name. And when you uploading the apk to store play stores signes it again with another signature. And I think android searches for that signature and when it can’t find it, it gives you warning message.

It’s possible that I’m not understanding something but here’s how I though this works:

Without a signing key (Or when using Unity’s debug signing key) Android would claim an app to be unsafe but would let you install the app. However once you got a signing key android would still tell you to me careful, but wouldn’t give you several warning messages about installing the apk file.

But this doesn’t appear to be the case, I just created a signing key through Unity and I can even verify the key is active when looking at the apk on Virustotal.

For example, when I install an application called NewPipe this is the only message I get before install or updating the app. (I just noticed it’s mentioning updating the application. That’s because I already have the app installed, but even when that app wasn’t installed the message looks very similar to this and there is still only 1 warning)

But when I try to install my own application, with or without a signing key, I get the message I got above with Newpipe, then I get this message:

If both apps have their own signing key, why does Newpipe only show one warning, while my app shows several?