@Lost_N_BIOS Can you change the VBIOS for both Gigabyte GA-J3455N-D3H and Asrock Asrock J3455-ITX so that I can use Intel VGA driver. I found the driver which was written for the chip but Intel encrypt the BIOS to prevent people to modify. There is a way to load it by first:
- Change Video to Legacy in BIOS then install the driver.
- After that, change the Video to UEFI from BIOS or it will crash when booting. However, when booting by doing this, the screen is black for 10-20 seconds, users don't know what going on. There is no more custom animation. There is an Intel NUC board which is using the same CPU but does not have this problem.

Sorry, I don't know anything about modifying drivers, I only know about working on BIOS.
If you want to use vBIOS, you cannot change to UEFI, that is GOP not vBIOS. You also cannot use Video in legacy mode, with BIOS in UEFI mode, unless you enable CSM first and then set video to legacy (This would be vBIOS)
None of that ^^ has anything to do with drivers.

I can update vBIOS for you, sounds like that is what you need? If that does not fix it, nothing you can do about the blank display at startup, tell them to wait and who cares
They do not need to see boot logo to use system! The only other way to fix that, if this fails to help, is to use a new/modern graphics card, and sometimes that may or may not help too (and or may need updated GOP)


Did you test booting in UEFI Mode, with Video set to UEFI Too? That would be UEFI and GOP boot mode..
Sorry, above is VERY confusing, now I think you are booting UEFI + GOP already, please confirm how you are booting and why, and what happens the other way.
The way you describe your last line above, that is UEFI + GOP, nothing to do with vBIOS