lumina-xconfig does not show resolution of the current screen; does not allow to add a new screen

[andreygrozin]

It's lumina-2.6.2 on Gentoo linux. I run lumina-xconfig. Resolution:, Rotation:, Primary screen are all grey. After Resolution:, the resolution of the current screen is not written, the field is empry. After Rotation:, the word None is written in grey. The checkbox Primary Screen is not checked, and it is not possible to check it.
The tabs Add Screen and Profiles are grey, it is not possible to switch to them.
If I run lumina-xconfig as root, nothing changes.
I definitely remember that many years ago everything worked. After connecting a projector to my notebook, I was able to add a new screen for it, and used it to deliver lectures to students. I'm not sure what version of lumina was installed on my notebook back then. Now this does not work.