bitbake rpi-test-image with MACHINE=raspberrypi3-64 failing to build on the zeus release of yocto - raspberry-pi3

Question

I'm following the readthedocs instructions for the meta-raspberrypi layer and trying to build the rpi-test-image image for the raspberrypi3-64 machine contained in the meta-raspberrypi layer using the zeus release of yocto.
I added this to conf/local.conf:
MACHINE ??= "raspberrypi3-64"
ENABLE_UART = "1"
My bblayers.conf file looks like this:
/opt/yocto/workspace/rpi3-64-build/conf[master]☢ ☠$ cat bblayers.conf
# POKY_BBLAYERS_CONF_VERSION is increased each time build/conf/bblayers.conf
# changes incompatibly
POKY_BBLAYERS_CONF_VERSION = "2"
BBPATH = "${TOPDIR}"
BBFILES ?= ""
BBLAYERS ?= " \
/opt/yocto/workspace/sources/poky/meta \
/opt/yocto/workspace/sources/poky/meta-poky \
/opt/yocto/workspace/sources/poky/meta-yocto-bsp \
/opt/yocto/workspace/sources/meta-openembedded/meta-oe \
/opt/yocto/workspace/sources/meta-openembedded/meta-multimedia \
/opt/yocto/workspace/sources/meta-openembedded/meta-networking \
/opt/yocto/workspace/sources/meta-openembedded/meta-python \
/opt/yocto/workspace/sources/meta-raspberrypi \
"
I added the 4 items from meta-openembeeded as a work-around for ERROR: Nothing RPROVIDES 'bigbuckbunny-480p':
This enables the build to run but it exits with the following errors:
/opt/yocto/workspace/rpi3-64-build/conf[master]☢ ☠$ bitbake rpi-test-image
Parsing recipes: 100% |#########################################################################################################################################| Time: 0:02:49
Parsing of 2340 .bb files complete (0 cached, 2340 parsed). 3464 targets, 133 skipped, 0 masked, 0 errors.
NOTE: Resolving any missing task queue dependencies
Build Configuration:
BB_VERSION = "1.44.0"
BUILD_SYS = "x86_64-linux"
NATIVELSBSTRING = "ubuntu-16.04"
TARGET_SYS = "aarch64-poky-linux"
MACHINE = "raspberrypi3-64"
DISTRO = "poky"
DISTRO_VERSION = "3.0.2"
TUNE_FEATURES = "aarch64 cortexa53 crc"
TARGET_FPU = ""
meta
meta-poky
meta-yocto-bsp = "zeus:74f229160c7f4037107c1dad8f0d02128c080a7e"
meta-oe
meta-multimedia
meta-networking
meta-python = "zeus:9e60d30669a2ad0598e9abf0cd15ee06b523986b"
meta-raspberrypi = "zeus:0e05098853eea77032bff9cf81955679edd2f35d"
Initialising tasks: 100% |######################################################################################################################################| Time: 0:00:06
Sstate summary: Wanted 1338 Found 0 Missed 1338 Current 0 (0% match, 0% complete)
NOTE: Executing Tasks
NOTE: Setscene tasks completed
WARNING: icu-native-64.2-r0 do_fetch: Checksum mismatch for local file /opt/yocto/cache/downloads/icu4c-64_2-src.tgz
Cleaning and trying again.
WARNING: icu-native-64.2-r0 do_fetch: Renaming /opt/yocto/cache/downloads/icu4c-64_2-src.tgz to /opt/yocto/cache/downloads/icu4c-64_2-src.tgz_bad-checksum_abb12cb25a05198ad8f4c1e6f668fa05
WARNING: icu-native-64.2-r0 do_fetch: Checksum failure encountered with download of http://download.icu-project.org/files/icu4c/64.2/icu4c-64_2-src.tgz - will attempt other sources if available
ERROR: rpi-test-image-1.0-r0 do_rootfs: Could not invoke dnf. Command '/opt/yocto/workspace/rpi3-64-build/tmp/work/raspberrypi3_64-poky-linux/rpi-test-image/1.0-r0/recipe-sysroot-native/usr/bin/dnf -v --rpmverbosity=info -y -c /opt/yocto/workspace/rpi3-64-build/tmp/work/raspberrypi3_64-poky-linux/rpi-test-image/1.0-r0/rootfs/etc/dnf/dnf.conf --setopt=reposdir=/opt/yocto/workspace/rpi3-64-build/tmp/work/raspberrypi3_64-poky-linux/rpi-test-image/1.0-r0/rootfs/etc/yum.repos.d --installroot=/opt/yocto/workspace/rpi3-64-build/tmp/work/raspberrypi3_64-poky-linux/rpi-test-image/1.0-r0/rootfs --setopt=logdir=/opt/yocto/workspace/rpi3-64-build/tmp/work/raspberrypi3_64-poky-linux/rpi-test-image/1.0-r0/temp --repofrompath=oe-repo,/opt/yocto/workspace/rpi3-64-build/tmp/work/raspberrypi3_64-poky-linux/rpi-test-image/1.0-r0/oe-rootfs-repo --nogpgcheck install psplash-raspberrypi packagegroup-core-boot packagegroup-base-extended run-postinsts packagegroup-rpi-test locale-base-en-us locale-base-en-gb' returned 1:
DNF version: 4.2.2
cachedir: /opt/yocto/workspace/rpi3-64-build/tmp/work/raspberrypi3_64-poky-linux/rpi-test-image/1.0-r0/rootfs/var/cache/dnf
Added oe-repo repo from /opt/yocto/workspace/rpi3-64-build/tmp/work/raspberrypi3_64-poky-linux/rpi-test-image/1.0-r0/oe-rootfs-repo
repo: using cache for: oe-repo
not found other for:
not found modules for:
not found deltainfo for:
not found updateinfo for:
oe-repo: using metadata from Thu 30 Apr 2020 09:25:08 PM UTC.
Last metadata expiration check: 0:00:02 ago on Thu 30 Apr 2020 09:25:11 PM UTC.
No module defaults found
--> Starting dependency resolution
--> Finished dependency resolution
Error:
Problem: package packagegroup-base-wifi-1.0-r83.raspberrypi3_64 requires wireless-regdb-static, but none of the providers can be installed
- package wireless-regdb-2019.06.03-r0.noarch conflicts with wireless-regdb-static provided by wireless-regdb-static-2019.06.03-r0.noarch
- package packagegroup-base-1.0-r83.raspberrypi3_64 requires packagegroup-base-wifi, but none of the providers can be installed
- package packagegroup-rpi-test-1.0-r0.noarch requires wireless-regdb, but none of the providers can be installed
- package packagegroup-base-extended-1.0-r83.raspberrypi3_64 requires packagegroup-base, but none of the providers can be installed
- conflicting requests
(try to add '--allowerasing' to command line to replace conflicting packages or '--skip-broken' to skip uninstallable packages or '--nobest' to use not only best candidate packages)
ERROR: Logfile of failure stored in: /opt/yocto/workspace/rpi3-64-build/tmp/work/raspberrypi3_64-poky-linux/rpi-test-image/1.0-r0/temp/log.do_rootfs.23419
ERROR: Task (/opt/yocto/workspace/sources/meta-raspberrypi/recipes-core/images/rpi-test-image.bb:do_rootfs) failed with exit code '1'
NOTE: Tasks Summary: Attempted 3511 tasks of which 1 didn't need to be rerun and 1 failed.
Summary: 1 task failed:
/opt/yocto/workspace/sources/meta-raspberrypi/recipes-core/images/rpi-test-image.bb:do_rootfs
Summary: There were 3 WARNING messages shown.
Summary: There was 1 ERROR message shown, returning a non-zero exit code.
/opt/yocto/workspace/rpi3-64-build/conf[master]☢ ☠$
I'm not even sure how to go about debugging it.
I've tried googling the warnings and error messages but was not able to find anything the might be causing the problem.
2 questions:
1: What might the problem be in this particular instance?
2: What is a good general procedure for debugging failed builds like this?
UPDATE: "bitbake core-image-base" does successfully build the image, but it is still unclear to me why "bitbake rpi-test-image" failed.