The codebase supports building against Qt6. Reproducible: Always
From https://gitlab.com/CalcProgrammer1/OpenRGB/-/blob/master/Documentation/Compiling.md - "When installing the QT toolset select the latest revision of Qt 5.15.x as OpenRGB is not yet compatible with QT6."
Maybe not all plugins are compatible yet? The main project builds and runs with Qt 6.7.3 just fine.