Problem solved by our own efforts. Thank you all for your interest and support. For future generations 😊 I will list the procedure here.
1. disconnect from the internet - otherwise the installer will prevent you from installing with a message that you have been temporarily blocked from access for security reasons - contact Adobe support for more information (unfortunately this is a false message due to the end of support for this program)
2. At the point when the installer offers you 2 options, back and log in, choose to log in even if you are disconnected from the internet. When you click on log in, you will be offered the option of logging in later. When you click on log in later, it will start installing the program - yay.
3. After the installation, the program still won't run because an older version of the program - Adobe installation manager - prevents it from running when you reconnect to the internet, updating to the Adobe Creative Cloud version.
4. After updating this manager, log in with your usual ACC credentials and Lightroom 6.14 will launch. Three cheers. 😊
Instructions have been machine translated from Czech
Thanks again for your interest and willingness to help.