Now it's error'ing thusly, but seems to be past the package problem:
Generate local signing keys...
Generate local certificate...
Package list missing or not up-to-date, generating it.
Building package index...
Downloading https://downloads.openwrt.org/snapshots/targets/mediatek/filogic/packages/Packages.gz
Updated list of available packages in /builder/build_dir/target-aarch64_cortex-a53_musl/root-mediatek/../../../../builder/dl/openwrt_core
Downloading https://downloads.openwrt.org/snapshots/targets/mediatek/filogic/packages/Packages.sig
Signature check passed.
Downloading https://downloads.openwrt.org/snapshots/packages/aarch64_cortex-a53/base/Packages.gz
Updated list of available packages in /builder/build_dir/target-aarch64_cortex-a53_musl/root-mediatek/../../../../builder/dl/openwrt_base
Downloading https://downloads.openwrt.org/snapshots/packages/aarch64_cortex-a53/base/Packages.sig
Signature check passed.
Downloading https://downloads.openwrt.org/snapshots/targets/mediatek/filogic/kmods/6.6.36-1-f492dffe00c0a7786964bab6d7e76015/Packages.gz
Updated list of available packages in /builder/build_dir/target-aarch64_cortex-a53_musl/root-mediatek/../../../../builder/dl/openwrt_kmods
Downloading https://downloads.openwrt.org/snapshots/targets/mediatek/filogic/kmods/6.6.36-1-f492dffe00c0a7786964bab6d7e76015/Packages.sig
Signature check passed.
Downloading https://downloads.openwrt.org/snapshots/packages/aarch64_cortex-a53/luci/Packages.gz
Updated list of available packages in /builder/build_dir/target-aarch64_cortex-a53_musl/root-mediatek/../../../../builder/dl/openwrt_luci
Downloading https://downloads.openwrt.org/snapshots/packages/aarch64_cortex-a53/luci/Packages.sig
Signature check passed.
Downloading https://downloads.openwrt.org/snapshots/packages/aarch64_cortex-a53/packages/Packages.gz
Updated list of available packages in /builder/build_dir/target-aarch64_cortex-a53_musl/root-mediatek/../../../../builder/dl/openwrt_packages
Downloading https://downloads.openwrt.org/snapshots/packages/aarch64_cortex-a53/packages/Packages.sig
Signature check passed.
Downloading https://downloads.openwrt.org/snapshots/packages/aarch64_cortex-a53/routing/Packages.gz
Updated list of available packages in /builder/build_dir/target-aarch64_cortex-a53_musl/root-mediatek/../../../../builder/dl/openwrt_routing
Downloading https://downloads.openwrt.org/snapshots/packages/aarch64_cortex-a53/routing/Packages.sig
Signature check passed.
Downloading https://downloads.openwrt.org/snapshots/packages/aarch64_cortex-a53/telephony/Packages.gz
Updated list of available packages in /builder/build_dir/target-aarch64_cortex-a53_musl/root-mediatek/../../../../builder/dl/openwrt_telephony
Downloading https://downloads.openwrt.org/snapshots/packages/aarch64_cortex-a53/telephony/Packages.sig
Signature check passed.
Downloading file:packages/Packages
Updated list of available packages in /builder/build_dir/target-aarch64_cortex-a53_musl/root-mediatek/../../../../builder/dl/imagebuilder
Downloading file:packages/Packages.sig
Signature check passed.
Pseudo file "dev" exists in source filesystem "/builder/build_dir/target-aarch64_cortex-a53_musl/root-mediatek/dev".
Ignoring, exclude it (-e/-ef) to override.
make[3]: *** No rule to make target 'glinet_gl-mt3000-initramfs-images', needed by '/builder/build_dir/target-aarch64_cortex-a53_musl/linux-mediatek_filogic/tmp/openwrt-f1453082aebf-mediatek-filogic-glinet_gl-mt3000-squashfs-sysupgrade.bin'. Stop.
make[2]: *** [Makefile:247: build_image] Error 2
make[1]: *** [Makefile:153: _call_image] Error 2
make: *** [Makefile:310: image] Error 2