stable30 does not work: Could not find a valid Nextcloud source in /var/www/html

Steps to reproduce:

rm -rf nextcloud-docker-dev # It's a clean installation
git clone https://github.com/juliusknorr/nextcloud-docker-dev
cd nextcloud-docker-dev
./bootstrap.sh
docker compose up stable30

Logs:

Attaching to stable30-1
stable30-1  | <Directory "/var/www/html">
stable30-1  | AllowOverride None
stable30-1  | RewriteEngine On
stable30-1  | RewriteBase /
stable30-1  | RewriteCond %{REQUEST_URI} !/installing.html$
stable30-1  | RewriteRule .* /installing.html [L]
stable30-1  | </Directory>
stable30-1  | =======================================================================================
stable30-1  |  🚨 Could not find a valid Nextcloud source in /var/www/html
stable30-1  |  Double check your REPO_PATH_SERVER and STABLE_ROOT_PATH environment variables in .env
stable30-1  | =======================================================================================
stable30-1  | 📰 Watching log file
stable30-1  | ⌚ Starting cron
stable30-1  | 🚀 Starting apache
stable30-1  | ==> /var/www/html/data/nextcloud.log <==
stable30-1  |
stable30-1  | ==> /var/log/cron/nextcloud.log <==
stable30-1  |
stable30-1  | ==> /var/log/xdebug.log <==
stable30-1  | [Fri Jan 17 21:46:56.787264 2025] [mpm_prefork:notice] [pid 1:tid 1] AH00163: Apache/2.4.62 (Debian) PHP/8.1.31 configured -- resuming normal operations
stable30-1  | [Fri Jan 17 21:46:56.787288 2025] [core:notice] [pid 1:tid 1] AH00094: Command line: 'apache2 -D FOREGROUND'

The normal nextcloud stack (docker compose up nextcloud) does not print this, but it gives me 503 service unavailable

Version: efff3c474b846640b0e0f55b90be8e0242ded768

Start with bootstrap.sh and the stable30 service invoked by docker compose, then inspect the REPO_PATH_SERVER and STABLE_ROOT_PATH values in .env referenced by the error. Reproduce the clean installation and compare it with the nextcloud stack; done means stable30 finds a valid Nextcloud source and the normal stack no longer returns 503.