Can A311D use only HDMI display at first boot ?

Dear MNT Community

This is my first post,
I’ve checked posts once,
but I apologize if this is a problem that has already been solved.

My classic MNT reform was LS1028A and motherboard v1.0.
This had broken because of LS1028A and/or motherboard v1.0, probably.
Now I bought motherboard v3.0 and A311D CPU module.

Now I have two problem & questions.

(1)
I don’t have MIPI DSI cable (LS1028A module & A311D module don’t include this).
So, can I buy MIPI DSI cable ? (if possible two for backup)

(2)
I try remove Display Cable form motherboard
and insert cable to HDMI port form outside monitor,
but balnk screen continues.
So, “at first boot,” how can I use only HDMI display without internal display.
Or please tell me commands to change internal display to HDMI display in bash with blank screen.

I read “Switching between HDMI and internal display on A311D.”
But in my situation, I can’t yet setup network and apt etc.

I would really appreciate any advice you can give me.
Thank you in advance.
This is a great machine and I’d like to fix it somehow.

Regards, Wataru TAKAHASHI