EDIT: possibly related to https://github.com/openwrt/asu/issues/515?
Anyway, I withdraw my "signature problem" comment - I just noticed it wasn't complaining about the Packages (aka, base) repo, but rather about the imagebuilder, which should probably be fine.
OP: Seems to be a signature problem:
Downloading file:packages/Packages
Updated list of available packages in /home/aparcar/asu/worker1/cache/23.05.0-rc1/mediatek/mt7622/build_dir/target-aarch64_cortex-a53_musl/root-mediatek/../../../../../../../../../../../home/aparcar/asu/worker1/cache/23.05.0-rc1/mediatek/mt7622/dl/imagebuilder
Downloading file:packages/Packages.sig
Signature check failed.
Remove wrong Signature file.
Package list missing or not up-to-date, generating it.
Building package index...
Downloading https://downloads.openwrt.org/releases/23.05.0-rc1/targets/mediatek/mt7622/packages/Packages.gz
Updated list of available packages in /home/aparcar/asu/worker1/cache/23.05.0-rc1/mediatek/mt7622/build_dir/target-aarch64_cortex-a53_musl/root-mediatek/../../../../../../../../../../../home/aparcar/asu/worker1/cache/23.05.0-rc1/mediatek/mt7622/dl/openwrt_core
Downloading https://downloads.openwrt.org/releases/23.05.0-rc1/targets/mediatek/mt7622/packages/Packages.sig
Signature check passed.
Downloading https://downloads.openwrt.org/releases/23.05.0-rc1/packages/aarch64_cortex-a53/base/Packages.gz
Updated list of available packages in /home/aparcar/asu/worker1/cache/23.05.0-rc1/mediatek/mt7622/build_dir/target-aarch64_cortex-a53_musl/root-mediatek/../../../../../../../../../../../home/aparcar/asu/worker1/cache/23.05.0-rc1/mediatek/mt7622/dl/openwrt_base
Downloading https://downloads.openwrt.org/releases/23.05.0-rc1/packages/aarch64_cortex-a53/base/Packages.sig
Signature check passed.
Downloading https://downloads.openwrt.org/releases/23.05.0-rc1/packages/aarch64_cortex-a53/luci/Packages.gz
Updated list of available packages in /home/aparcar/asu/worker1/cache/23.05.0-rc1/mediatek/mt7622/build_dir/target-aarch64_cortex-a53_musl/root-mediatek/../../../../../../../../../../../home/aparcar/asu/worker1/cache/23.05.0-rc1/mediatek/mt7622/dl/openwrt_luci
Downloading https://downloads.openwrt.org/releases/23.05.0-rc1/packages/aarch64_cortex-a53/luci/Packages.sig
Signature check passed.
Downloading https://downloads.openwrt.org/releases/23.05.0-rc1/packages/aarch64_cortex-a53/packages/Packages.gz
Updated list of available packages in /home/aparcar/asu/worker1/cache/23.05.0-rc1/mediatek/mt7622/build_dir/target-aarch64_cortex-a53_musl/root-mediatek/../../../../../../../../../../../home/aparcar/asu/worker1/cache/23.05.0-rc1/mediatek/mt7622/dl/openwrt_packages
Downloading https://downloads.openwrt.org/releases/23.05.0-rc1/packages/aarch64_cortex-a53/packages/Packages.sig
Signature check passed.
Downloading https://downloads.openwrt.org/releases/23.05.0-rc1/packages/aarch64_cortex-a53/routing/Packages.gz
Updated list of available packages in /home/aparcar/asu/worker1/cache/23.05.0-rc1/mediatek/mt7622/build_dir/target-aarch64_cortex-a53_musl/root-mediatek/../../../../../../../../../../../home/aparcar/asu/worker1/cache/23.05.0-rc1/mediatek/mt7622/dl/openwrt_routing
Downloading https://downloads.openwrt.org/releases/23.05.0-rc1/packages/aarch64_cortex-a53/routing/Packages.sig
Signature check passed.
Downloading https://downloads.openwrt.org/releases/23.05.0-rc1/packages/aarch64_cortex-a53/telephony/Packages.gz
Updated list of available packages in /home/aparcar/asu/worker1/cache/23.05.0-rc1/mediatek/mt7622/build_dir/target-aarch64_cortex-a53_musl/root-mediatek/../../../../../../../../../../../home/aparcar/asu/worker1/cache/23.05.0-rc1/mediatek/mt7622/dl/openwrt_telephony
Downloading https://downloads.openwrt.org/releases/23.05.0-rc1/packages/aarch64_cortex-a53/telephony/Packages.sig
Signature check passed.
Downloading file:packages/Packages
Updated list of available packages in /home/aparcar/asu/worker1/cache/23.05.0-rc1/mediatek/mt7622/build_dir/target-aarch64_cortex-a53_musl/root-mediatek/../../../../../../../../../../../home/aparcar/asu/worker1/cache/23.05.0-rc1/mediatek/mt7622/dl/imagebuilder
Downloading file:packages/Packages.sig
Signature check failed.
Remove wrong Signature file.
Collected errors:
* pkg_hash_check_unresolved: cannot find dependency libubox20220927 for mtd
* pkg_hash_fetch_best_installation_candidate: Packages for mtd found, but incompatible with the architectures configured
* opkg_install_cmd: Cannot install package mtd.
* satisfy_dependencies_for: Cannot satisfy the following dependencies for mtd:
* libubox20220927
* opkg_install_cmd: Cannot install package mtd.
make[2]: *** [Makefile:186: package_install] Error 255
make[1]: *** [Makefile:151: _call_manifest] Error 2
make: *** [Makefile:271: manifest] Error 2
EDIT: possibly related to https://github.com/openwrt/asu/issues/515? Anyway, I withdraw my "signature problem" comment - I just noticed it wasn't complaining about the Packages (aka, base) repo, but rather about the imagebuilder, which should probably be fine.
OP: Seems to be a signature problem:
Full sysupgrade output: Request Data:
STDERR: