Seems like you’re nesting virtualization too much. Stick with 1 level of virtualization. If it’s a server, I’d use proxmox on bare metal. Its a server so split services per VM/container. Install OMV on its own VM. Another for docker, with docker services ran by a non root user.

What other federated platforms do you look into? Most of the the reddit communities I use to be a part of are super tiny on lemmy.

Can I get more details on this captive portal? How does it diagnose network issues or what software are you using for the captive portal?