Here is what happened.
No issue with reinstallation of Sonoma 14.4.1 on my M1 2020 MacBook Air. An external monitor was assigned as the main display. However the external monitor received "No Signal" during re-installation process and the in-built display was working well. The re-installation took about 1h.
The immediate trial to start-up after shutdown using in-built display was a success.
However the next day brought sad news.
a) Start up using in-built display took 4'6" to get to the login page. I did not touch any keys. The colourful globe was rotating until the screen lights up. Re-start was fast.
b) Start up using external monitor as main display took 3'33"
c) Start up using in-built display took 3'39"
So good news is, it starts up
Bad news is, it takes a long time to start up
Is there a bug in Sonoma 14.4.1?
What next?