serial write can't do it myself

[Larz60+]

I didn't think it would be helpful

Perhaps you're correct, at least on a high level. I have interfaced to
simpler devices, and knew that there are a series of commands that
must be sent, correctly, in proper order, before anything would be
seen on the device.
From the Nextion Instruction set manual:

Note: Nextion will remain waiting at step 5 until every byte of specified quantity is received.

so I suspect this is why you're not seeing anything

Have you seen this: https://github.com/g4klx/MMDVMHost
This appears to be a complete interface to one of their displays.

Another page http://vorsselmansphilip.blogspot.com/20...-test.html

and one final:
http://www.marrold.co.uk/2017/03/adding-...mhost.html