At least one valid and activated repository is required to successfully complete this action

Question

I tried to create an online installer for my project. While running the online installer, I get a error message:

At least one valid and activated repository is required to successfully complete this action.

What is not yet clear to me: What form must the URL have? The Qt documentation states that the link should point to the Updates.xml; however, the links without Updates.xml are specified at the end.

What form must the repository under the URL have? Does it have to be a Repository.git, or just a normal folder in which all files are located?

Command:

binarycreator.exe --online-only -c config\config.xml -p packages Installer.exe

package.xml:

<?xml version="1.0" encoding="UTF-8"?>
<Installer>
    <Name>TestInstaller</Name>
    <Version>1.0.0</Version>
    <Title>Installer</Title>
    <StartMenuDir>Test</StartMenuDir>
    <TargetDir>C:/Program Files (x86)/Test</TargetDir>
</Installer>
<RemoteRepositories>
<!-- All of these attemps (also with http://, login data in URL or in xml, doesn't work -->
     <Repository>
             <Url>https://http.omsi-tools.de/update/Updates.xml</Url>
             <Enabled>1</Enabled>
             <DisplayName>Att01</DisplayName>
     </Repository>
     <Repository>
             <Url>https://http.omsi-tools.de/update/</Url>
             <Enabled>1</Enabled>
             <DisplayName>Att02</DisplayName>
     </Repository>
     <Repository>
             <!-- According to https://stackoverflow.com/a/56655213/13100331 - doesn't work, even not without '/Updates.xml' or other URLs mentioned in this topic -->
             <Url>https://raw.githubusercontent.com/alexlyapin/Basic4x4/master/clientRepository/Updates.xml</Url>
             <Enabled>1</Enabled>
             <DisplayName>Att03-GitHub</DisplayName>
     </Repository>
</RemoteRepositories>