So, the root of my booting problem is Linux doesn’t yet fully support my intel core i5-10400 processor’s uhd 630 graphics.
I’ve been able to boot gentoo-sources-5.10.27 successfully using grub on my new Asus Tuf Gaming B560M-Plus Wifi board equipped with an intel core i5-10400 processor. If you use the nomodeset kernel parameter, the boot messages scrolling by on the screen look like what you’d expect from a normal grub/gentoo boot. If you don’t use nomodeset, a few initial lines of boot progress appear from grub, then stop. It looks like the boot has hung after the initrd, but it hasn’t. When the kernel takes over the display, something in the modesetting goes wrong, and nothing is displayed from that point on. But the system boots fine otherwise. You can’t start X11 even after following the instructions in https://wiki.gentoo.org/wiki/Xorg/Guide. The Xorg log indicates that it can’t find the proper driver. After searching for the errors reported in the Xorg log, I stumbled on the same problem I’m having in https://unix.stackexchange.com/questions/642535/xorg-detects-no-displays-with-an-intel-uhd-630. That article in turn refers to activity in https://cgit.freedesktop.org/drm-tip, which is the direct rendering manager development site. What I gather from poking around there is that the intel 915 video driver has just been patched to solve the problem I’m having, but uncertain whether the patch has made it out to the linux distros. The problem affects all intel processors with onboard uhd 630 graphics. I’ve tried gentoo-sources 5.10.27 and 5.11.21. Both have the video problem. I’ve also tried 5.12.4. Can’t get it to boot. Have also tried Ubuntu-20.04.2.0-desktop. It works fine on my older intel boxes, but displays the same video problem on my new board/cpu. Haven’t verified it, but guessing none of these have the uhd 630 patch. So, my previous suspects - secure boot, motherboard, grub, and my customized kernel configs - are all innocent and working fine. Just have to wait for the patched intel driver to show up in gentoo-sources. Thanks for all the helpful advice I received! Couldn’t have gotten this far without it. John