Hmm, so I'm still confused. I'm seeing similar trouble to the original poster here.
I've downloaded openwrt-imagebuilder-21.02.0-rc3-ipq806x-generic.Linux-x86_64.tar.xz from https://downloads.openwrt.org/releases/21.02.0-rc3/targets/ipq806x/generic/ (where everything is currently dated June 15th).
Using that image builder, I'm currently getting this failure from make manifest:
Collected errors:
* pkg_hash_check_unresolved: cannot find dependency libubus20210630 for netifd
* pkg_hash_fetch_best_installation_candidate: Packages for netifd found, but incompatible with the architectures configured
* pkg_hash_check_unresolved: cannot find dependency libubus20210630 for ubox
* pkg_hash_fetch_best_installation_candidate: Packages for ubox found, but incompatible with the architectures configured
* satisfy_dependencies_for: Cannot satisfy the following dependencies for base-files:
* libubus20210630
* opkg_install_cmd: Cannot install package base-files.
make manifest PROFILE=$PROFILE PACKAGES="$PACKAGES_NETGEAR" DISABLED_SERVICES="$DISABLED_SERVICES_HOME"
Downloading https://downloads.openwrt.org/releases/21.02.0-rc3/targets/ipq806x/generic/packages/Packages.gz
Updated list of available packages in /home/osboxes/openwrt-imagebuilder-21.02.0-rc3-ipq806x-generic.Linux-x86_64/build_dir/target-arm_cortex-a15+neon-vfpv4_musl_eabi/root-ipq806x/../../../../../../home/osboxes/openwrt-imagebuilder-21.02.0-rc3-ipq806x-generic.Linux-x86_64/dl/openwrt_core
Downloading https://downloads.openwrt.org/releases/21.02.0-rc3/targets/ipq806x/generic/packages/Packages.sig
Signature check passed.
Downloading https://downloads.openwrt.org/releases/21.02.0-rc3/packages/arm_cortex-a15_neon-vfpv4/base/Packages.gz
Updated list of available packages in /home/osboxes/openwrt-imagebuilder-21.02.0-rc3-ipq806x-generic.Linux-x86_64/build_dir/target-arm_cortex-a15+neon-vfpv4_musl_eabi/root-ipq806x/../../../../../../home/osboxes/openwrt-imagebuilder-21.02.0-rc3-ipq806x-generic.Linux-x86_64/dl/openwrt_base
Downloading https://downloads.openwrt.org/releases/21.02.0-rc3/packages/arm_cortex-a15_neon-vfpv4/base/Packages.sig
Signature check passed.
Downloading https://downloads.openwrt.org/releases/21.02.0-rc3/packages/arm_cortex-a15_neon-vfpv4/luci/Packages.gz
Updated list of available packages in /home/osboxes/openwrt-imagebuilder-21.02.0-rc3-ipq806x-generic.Linux-x86_64/build_dir/target-arm_cortex-a15+neon-vfpv4_musl_eabi/root-ipq806x/../../../../../../home/osboxes/openwrt-imagebuilder-21.02.0-rc3-ipq806x-generic.Linux-x86_64/dl/openwrt_luci
Downloading https://downloads.openwrt.org/releases/21.02.0-rc3/packages/arm_cortex-a15_neon-vfpv4/luci/Packages.sig
Signature check passed.
Downloading https://downloads.openwrt.org/releases/21.02.0-rc3/packages/arm_cortex-a15_neon-vfpv4/packages/Packages.gz
Updated list of available packages in /home/osboxes/openwrt-imagebuilder-21.02.0-rc3-ipq806x-generic.Linux-x86_64/build_dir/target-arm_cortex-a15+neon-vfpv4_musl_eabi/root-ipq806x/../../../../../../home/osboxes/openwrt-imagebuilder-21.02.0-rc3-ipq806x-generic.Linux-x86_64/dl/openwrt_packages
Downloading https://downloads.openwrt.org/releases/21.02.0-rc3/packages/arm_cortex-a15_neon-vfpv4/packages/Packages.sig
Signature check passed.
Downloading https://downloads.openwrt.org/releases/21.02.0-rc3/packages/arm_cortex-a15_neon-vfpv4/routing/Packages.gz
Updated list of available packages in /home/osboxes/openwrt-imagebuilder-21.02.0-rc3-ipq806x-generic.Linux-x86_64/build_dir/target-arm_cortex-a15+neon-vfpv4_musl_eabi/root-ipq806x/../../../../../../home/osboxes/openwrt-imagebuilder-21.02.0-rc3-ipq806x-generic.Linux-x86_64/dl/openwrt_routing
Downloading https://downloads.openwrt.org/releases/21.02.0-rc3/packages/arm_cortex-a15_neon-vfpv4/routing/Packages.sig
Signature check passed.
Downloading https://downloads.openwrt.org/releases/21.02.0-rc3/packages/arm_cortex-a15_neon-vfpv4/telephony/Packages.gz
Updated list of available packages in /home/osboxes/openwrt-imagebuilder-21.02.0-rc3-ipq806x-generic.Linux-x86_64/build_dir/target-arm_cortex-a15+neon-vfpv4_musl_eabi/root-ipq806x/../../../../../../home/osboxes/openwrt-imagebuilder-21.02.0-rc3-ipq806x-generic.Linux-x86_64/dl/openwrt_telephony
Downloading https://downloads.openwrt.org/releases/21.02.0-rc3/packages/arm_cortex-a15_neon-vfpv4/telephony/Packages.sig
Signature check passed.
So it seems to me there's an incompatibility between the RC3 built on June 15th (targets and core packages) and newer builds of RC3 content built on July 1st.
Is there some build-bot work needed to rebuild the rc3 targets? Or should it rebuild the rc3 packages using original target dependencies?
What's currently published as -rc3 is not a working set of targets + packages.
The RC3 images point to the snapshot directories for downloading packages, leading to inevitable conflicts as the snapshots track OpenWRT github changes.
Index of (root) / releases / 21.02.0-rc3 /
File Name File Size Date
packages/ -> ../packages-21.02 - Sat Jul 3 13:14:23 2021
targets/ - Wed Jun 16 03:49:13 2021