Very straight forward. When systemd is selected as the init system, and BR2_TARGET_GENERIC_GETTY_PORT is set to console, two gettys are spawned which prevents a user from logging in. How to reproduce: make qemu_x86_64_defconfig menuconfig -> System configuration -> Init system -> systemd make Then run the resulting image.
I can confirm I see similar with aarch64 build using master. I noticed it is possible to login and run commands you just have to keep escaping the new getty :-)
After I did a quick google search I found a post on stack exchange that indicates this has been an issue since at least version 2019.02! https://unix.stackexchange.com/questions/566959/how-to-prevent-console-getty-service-to-start The logic behind /dev/console in systemd.mk is a bit complex and I am not sure where to start.
I have Jérémy Rosen to have a look, see http://lists.busybox.net/pipermail/buildroot/2020-May/282962.html. I must say the logic in systemd.mk is very confusing, and the comment above it doesn't help understand what's going on.
*** This bug has been marked as a duplicate of bug 12361 ***