RUN addgroup --gid 1001 nodejs; \
	adduser --uid 1001 nextjs

I think the adduser command is creating a user (nextjs) with a default group id of 1001, which has already been used in the previous statement.

RUN addgroup --gid 1009 foo;
RUN addgroup --gid 1001 nodejs;
RUN adduser  --uid 1001 --gid 1009 nextjs

This hack works but then I get a Composer could not find a composer.json file in /app error in the php container. Perhaps a volume not getting mounted.

Looks like this is fixed in main but I downloaded v4.1.0

SERVER_NAME=your-domain-name.example.com \
APP_SECRET=ChangeMe \
POSTGRES_PASSWORD=ChangeMe \
CADDY_MERCURE_JWT_SECRET=ChangeThisMercureHubJWTSecretKey \
docker compose -f compose.yaml -f compose.prod.yaml up --wait

It seems to me that this compose up command (from here) doesn't load either the pwa or php code into the containers. The volume definitions are in the override compose file, which isn't included (and would yield a dev environment anyway).