Debian's current Qt framework package maintainers decision on their own not to maintain the next significant branch which is scheduled for release in December. At the same time, maintenance of the previous branch of Qt 5 will continue without changes. Delivery of Qt 6 to Debian will be ensured if there are new maintainers who are ready to provide adequate support for packages with the new branch.
The reasons given are the lack of time to maintain quality packages with Qt 6. Qt has a very large amount of code, which requires a lot of time to maintain and build resources that current maintainers lack.
Separately, it is emphasized that the quality of the code and Qt Company is not affiliated with the decision.
Source: opennet.ru