Why "maybe-ubiquity" on default kernel command line?
Solution 1:
AFAIK this param resides in the DEFAULT commandline after one has installed the system from a LiveCD/DVD image.
Ubiquity is an installer system Ubuntu uses on the live systems, there seems to be a bug that keeps this param also in the default commandline after installation.
I think it's safe to remove from GRUB_CMDLINE_LINUX_DEFAULT.