KS 5.5 on Ubuntu 18.04 LTS: Currently, KS's GUI mode is not supported on Linux

I’ve downloaded and extracted Katalon_Studio_Linux_64-5.5.tar.gz but if I try to run katalon executable it shows the notification “Currently, KS’s GUI mode is not supported on Linux…”
Environment: Ubuntu 18.04 LTS (64-bit GNOME 3.28.1), openjdk version 1.8.0_171

No this is not a bug. Official version from Download page is non-UI version, so that’s why you see that error message. GUI version is still in Beta phase and it’s not uploaded yet to Download page (we will plan to have it soon).