Thank you for raising this, as Morag says, .deb packages are available for all releases from 9.1 onwards.
It would appear that not all references to using rpm --force-debian were correctly removed at that point: I have asked our docs team to review these pages and make the necessary edits.
For reference, assuming you're looking for amd64 architecture, the most recent LTS .deb client package is 9.4.0.15-IBM-MQC-UbuntuLinuxX64, and the most recent CD package is 9.4.4.0-IBM-MQC-UbuntuLinuxX64 . Other levels and architectures are also available on Fix Central.
If you would prefer not to install at all, there is also the unzippable redist package, eg. 9.4.4.0-IBM-MQC-Redist-LinuxX64 (note there's no Ubuntu version here, because it's just an unzip applicable to all supported Linuxes)