Use Multisite

After running Tools > Network setup in the Wordpress admin, instead of following Wordpress requirements, add settings directly in your environment ( .env.local )

WP_MULTISITE=1
SUBDOMAIN_INSTALL=0
SITE_ID_CURRENT_SITE=1
BLOG_ID_CURRENT_SITE=1

Not working ? In some cases, instead of WP_MULTISITE=1, you may need to add your main domain WP_MULTISITE=demo.wordpress-bundle.com