The T1C JS SDK no longer has a method to download the T1C installer.
Instead, the T1C installer can be downloaded by navigating the client browser to the /v3/downloads/installer endpoint of the Distribution Service (e.g. https://acc-ds.t1t.io/v3/downloads/installer). The Distribution Service will analyse the User-Agent header and automatically initiate the download of an OS-appropriate installer of the latest configured version. The user agent string parsing is considered "best-effort"; as they can vary wildly depending OS and browser software.
Alternatively, you can also initiate the download of a T1C installer with the following endpoints:
/v3/downloads/installers/{{OS}}: This endpoint allows you to specify the OS for which you wish to obtain an installer. The possible values are win32, win64, unix, macosmacosarm.