I would like to run a Wikibase instance in my Raspberry Pi 4 for demo/sandbox purposes.
I'm trying to generate a Wikibase docker image for ARM 64 bits, using a Raspberry Pi 4 (ARMv8) but I get this error:

+ docker run --volume /tmp/tmp.dBLABg/Wikibase/composer.json:/tmp/composer.json --volume /tmp/tmp.dBLABg/Wikibase/vendor/:/tmp/vendor/ docker-registry.wikimedia.org/releng/composer-php73:latest install --no-dev --ignore-platform-reqs -vv -d /tmp/
WARNING: The requested image's platform (linux/amd64) does not match the detected host platform (linux/arm64/v8) and no specific platform was requested
standard_init_linux.go:228: exec user process caused: exec format error

Then I need a "docker-registry.wikimedia.org/releng/composer-php73" image for ARM, where could I find the source code to generate this image from scratch?