Downloading Manager from other sites risks infecting your system with a virus and they are not as well maintained as the actual download site https://www.manager.io/download/
White label version of Manager can be run however I believe that is a server version configuration not a desktop version.
The issue you are describing is a font display problem. It can be caused by
- not having the font installed or conflicting with a previously installed font
- browser and browser setting
- corruption of your Manger version
- operating system
To fault find you need to change significant parts of your set up such as
- install a clean version of manager on a clean computer
- try the cloud version
- Try other browser (which have you tried)