Created attachment 120880 [details] photo of the display unable to install KDE Neon on Acer C720 using image file neon-user-20190613-1123.iso installer crashes somewhere not far from the end of installation process.
checked sha-256. it is correct.
I think it was a problem with RealTimeClock. My laptop does not have backup battery for RTC so the readings from it are completely wrong if battery were removed for some time. I wrote some correct date-time into RTC and installation finished successfully.
The dialog mentions to report the issue with 'ubuntu-bug ubiquity'.