Wild guess !Is it that your keyboard is not working under Coreboot, so OPNsense installer does not detect any key presses; and only after OPNsense boots up fully, you get a working keyboard.
If you only see the login prompt you may have the wrong image type or the primary console will not redirect to your screen for whatever reason.I'm assuming you say that you still see the kernel boot messages but once init takes over no messages no questions for a while and then a login prompt?Cheers,Franco
It's quite clear, but a video would be more helpful at this point so we can talk about the same thing.
If you only see the login prompt you may have the wrong image type or the primary console will not redirect to your screen for whatever reason.I'm assuming you say that you still see the kernel boot messages but once init takes over no messages no questions for a while and then a login prompt?