Upstream has implemented Qt6 support long ago but is currently not able
to do a release due to their release process failing for Windows.

Please consider importing the commit
https://github.com/sqlitebrowser/sqlitebrowser/commit/21dd3b897e65075c445c6d349db87eb908d7a9be
from their stable v3.13.x branch as quilt patch and building with Qt6.
This would help with dropping Qt5 support from qscintilla2 package.