At some time this year, dosbox got broken, but it is unclear who to blame. They say it is the fault of the desktop or X server. Specifically, the mouse is not captured anymore, neither by clicking into the window nor by using Ctrl-F10. Instead, the title bar of the window becomes gray on my desktop, which means the window is unfocused, which is not true. Hence, I cannot use any DOS program with mouse anymore (all those antique games…).
I tried an earlier snapshot of 4.17 from June, but the problem was already there. Dosbox itself has not changed much in the last years, so it seems likely to me that there is an issue between the dosbox and the X server. I am using amdgpu.