Checking documentation for deb packages, I read that the control file should be UTF-8:
I was able to build a non-utf8 package using dpkg -b.
This was originally reported in Landscape-Client:
A possible workaround was provided by the user "Uli Köhler" at:
Making reference to the first version, '1.0.0.944' of the package "veeam". The report points:
"The strange character is the U+FFFD � REPLACEMENT CHARACTER."
I was able to reproduce the problem in Landscape Client, and I discovered the error came from a wrong encoding used in the control file.
I made a wrong encoded description, which reproduced the error on our side.
Nevertheless, it is not a bug in Landscape but in dpkg, which allowed building a deb package with a wrong encoded control file.
The broken description package is attached for further study.