Hi Chris,
thanks for you reply.
I believe, I found the culprit and solved the issue. (BTW: the “USB issue” came up with any update state)
An incorrect system time was set in the BIOS - you had previously noticed the journalctl logs the time /date jumps
Once I had synched BIOS time with my Linux system time, the boot delay disappeared, now it takes about 1 second longer with a USB device plugged in and total boot time seems OK for me.