Yes, manual installation is a way.
Just to explain the issue. ArchiCAD has one binary per localization and its folders structure is localized as well. This is not very common, because usually, there is one binary holding default language mutation ( eng usually ) and the user has the possibility to download other language packs remotely or select the mutation right from the installer. Even if a program has multiple language versions binaries, developers are trying to keep the names of the folders consistent...
In the INT localization addon folder is named Add-Ons but this is very different for your lang. mutation, therefore, our installer has problems to find the right folder ATM. This will be fixed later of course, but our primary language will be still INT version for the sake of the development.