When I execute equery or emerge in qemu-aarch64 chroot, I see the following error message many times.
Unable to configure loopback interface: Operation not supported
I traced the error back to _configure_loopback_interface function in sys-apps/portage by searching the internet.
Try setting FEATURES="-network-sandbox" in make.conf.
I suspect there is nothing we can do in Portage to make this with in qemu-user.
FEATURES="-network-sandbox" works around this issue. It seems qemu doesn't yet support pid-sandbox and network-sandbox