After many months, I seem to have solved my very long boot up times on Manjaro KDE
…Linux does not lower that flush threshold if it sees the RAM is more. Maybe it did and my older install did not get some updated config files. See https://www.blackmoreops.com/2014/09/22/linux-kernel-panic-issue-fix-hung_task_timeout_secs-blocked-120-seconds-problem/…