As this was suggested on another place I upgraded the BIOS of the notebook manually. After this upgrade the boot process takes a bit longer but the bug described above did not happen again (ca. 30 boots up to now).
Preinstalled BIOS version: 301 (10/09/2018) New BIOS version: 307 (07/05/2019) The latest BIOS file is available at: https://www.asus.com/sg/Laptops /ASUS-ZenBook-Pro-14-UX480FD/HelpDesk_BIOS/ Manual how to upgrade the BIOS on a ASUS: https://www.asus.com/en/support/FAQ/1008859/ (Download the ZIP file, extract onto an empty USB stick, boot into BIOS configuration menue, select »Advanced« then »ASUS EZ Flash Utillity«, select the given file on the USB drive, start the upgrade, let the update reboot your system -> Important: All boot settings will be gone, disable »Fast Boot« & »Secure Boot« and switch from »RAID« drivers to AHCI drivers again) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1849448 Title: Boot frequently stuck on Asus ZenBook Pro 14 UX480 & Ubuntu 19.10 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1849448/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs