Problems returning from hibernate in KDE 4: blank screen

Since kernel 5.x was introduced in -current this problem is present. It is not a nuisance as I can recover the login screen by pressing Crtl+Alt+F2 and Ctrl_Alt+F7. I did not have the time to search for this problem until yesterday. I then compiled LTS kernel 4.14.171 and tested the system. All works fine. So, the problem was introduced in kernel 5.x family. I am now using kernel 4, no problem with that.

I would like to try to help to solve this problem by collecting the necessary data and send it to someone that understand the kernel fault reporting system better than I. Any volunteers ?