I just installed the latest build of Eoan and had this happen. I chose the install open, without trying the desktop. I had maximized the window and then clicked minimize by mistake instead of un-maximize. Alt+Tab didn't do anything. My workaround was to switch to another virtual terminal and kill kwin, after which the installer appeared without window decorations.
I just installed the latest build of Eoan and had this happen. I chose the install open, without trying the desktop. I had maximized the window and then clicked minimize by mistake instead of un-maximize. Alt+Tab didn't do anything. My workaround was to switch to another virtual terminal and kill kwin, after which the installer appeared without window decorations.