Meanwhile after some updates I manage to login even without power supply. After that the screen is distorted and looks like this - s. attachment. In the screen you see right a shadow - my taskbar. You can only see the top bar of windows.
** Attachment added: "IMG_20200414_230842.jpg" https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-amdgpu/+bug/1872452/+attachment/5354178/+files/IMG_20200414_230842.jpg -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1872452 Title: [amdgpu] Boot into black screen without power supply (Kubuntu on AMD / Thinkpad T495) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/kwin/+bug/1872452/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs