I'm not using any of the tested software as containers within the VM. I've been installing ubuntu 22.04 as a Proxmox container and doing the one line bash install command for runtipi/umbrel. Start9 is its own OS so that was installed on a Proxmox VM using their ISO.
I've tried both http & https on every attempt. But have not checked logs yet. I can see that for the docker based ones, running
Next I am going to try reinstalling Proxmox and set it to be on the Admin network to see if that changes the results. From what I remember, this is easier than trying to change the gateway on an already installed Proxmox system.