I never even heard of Collabora, and so I didn’t understand what the point of it all was, but maybe this sums it up.

https://en.wikipedia.org/wiki/LibreOffice

TDF [The Document Foundation] describes LibreOffice as intended for individual users, and encourages enterprises to obtain the software and technical support services from ecosystem partners like Collabora. TDF states that most development is carried out by these commercial partners in the course of supporting enterprise customers. This arrangement has contributed to a significantly higher level of development activity compared to Apache OpenOffice, another fork of OpenOffice.org, which has struggled since 2015 to attract and retain enough contributors to sustain active development and to provide timely security updates.

Enterprise and derivative versions

• Collabora Office and Collabora Online are enterprise-focussed editions of LibreOffice supporting online, mobile and desktop devices. And providing long-term support, technical support, custom features, and Service Level Agreements (SLA)s.

• ZetaOffice – developed by Allotropia, is a paid enterprise version offered as both a desktop application with long-term support and a web-based version using WebAssembly.

In the 2020s, the number of commercial partner organizations decreased. In June 2023, Red Hat announced it would no longer maintain LibreOffice packages in future releases of Red Hat Enterprise Linux. Maintenance of LibreOffice packages for the related Fedora Linux was transitioned to the Fedora LibreOffice Special Interest Group. In 2021, CIB [Computer Integrated Business] spun off its LibreOffice development and support services into a new company, Allotropia. In May 2025, Collabora announced the acquisition of Allotropia, intending to combine Allotropia's ZetaOffice and WebAssembly with its own Collabora Office and Collabora Online products.

But I still don’t understand why Collabora now has introduces a third flavor (Collabora [Online] Desktop) to the other two (Collabora Online and Collabora Office “Classic”) while LIbreOffice still has two (LibreOffice and LibreOffice Online).

Edit to add: https://www.collaboraonline.com/case-studies/differences-between-collabora-online-and-collabora-office/

Learn about the key differences between Collabora Online and Collabora Office and Collabora Office Classic, and how these products can work for you.