Okay, I apologize: I did not understand from the documentation that the name of the cgi file needed to appear in the web variable. The following fixes the error:

https://univ.domain/USER/support/roundup.cgi/support/

May I suggest clarifying the following comment in config.ini 

# The web address that the tracker is viewable at.
# This will be included in information sent to users of the tracker.
# The URL MUST include the cgi-bin part or anything else
# that is required to get to the home page of the tracker.
# You MUST include a trailing '/' in the URL.

to something like

# The web address that the tracker is viewable at.
# This will be included in information sent to users of the tracker.
# The URL MUST include the cgi-bin part or anything else
# that is required to get to the home page of the tracker,
# including the url elements including or following tracker.cgi (if applicable).
# You MUST include a trailing '/' in the URL.

Anyway, thanks for the great project.