How to disable IPv6 and/or enable IPv4

I’m trying out this project. First install on my home lab with a Debian 12 VM was smooth as silk.

Now I’m trying to install on a VM in GCP. First pass, everything seemed to work, but when I try to connect at port 80, turns out it’s only binding to tcp6.

Ok, then, I will create a fresh VM and disable IPv6 in GRUB before running the install script. Nope, now the install script finishes without errors, but none of the containers are listening on port 80. I searched the web and this forum, found one old solved issue on GitHub (related to same issue on Raspbian), and basically nothing else.

Anyone have a clue what I’m missing or otherwise doing wrong? I didn’t spot anything relevant in the log files.