As it seems latest launcher update + Feature Update to Windows 10, version 1809 made game client itself “unlaunchable” (last time when I logged in at 2019.02.07 everything was fine). Although I already filled bug report and sent all relevant log files, I wanted to know, who else beside me suffers from the same problem?
GM Mechanic advised me to (re)update my video drivers. My guess is the 1809 update killed what I had in place (slightly older GeForce drivers). Installed the latest from NVIDIA … and no joy :P. Rebooted, and all works fine.