Hi! The xca binary still links against Qt5 libraries, despite declaring Qt6 as a build dependency in Salsa commit 4eff3c03. This is due to missing debian/rules carrying an explicit declaration instructing cmake to select the Qt5 libraries. Specifically, this is debian/rules line 6, export QT_SELECT=qt5. Changing that to export QT_SELECT=qt6 allows correct build and operation on amd64, both for the existing 2.8.0 version, and for the latest 2.9.0 version. Thanks!
The above is still the case for 2.9.0-1, needs QT_SELECT=qt6 in debian/rules.