I’m hoping you just need to use wp-cli’s wp core multisite-install
as a final step:
# provision using server.yml
# deploy using deploy.yml or bin/deploy.sh
# SSH to server as the web user
$ ssh web@example.com
# Change to site directory
$ cd /srv/www/example.com/current
# Install WP multisite
$ wp core multisite-install --title="Title" --admin_user="username" --admin_password="password" --admin_email="you@domain.com"
If it outputs The network already exists
you could (backup data if you need it, then) wp db reset
and try the wp core multisite-install
again.
Then see if you can connect in the browser.
Let us know of any solution you may find so we can get it in the docs or fix it in the code.