Spin up Pi-hole high-availability `HA` for DNS lookup in LAN network

[1Copenut]

I'd like to use this as a chance to test Pi-hole on RaspianOS as a high-availability DNS lookup. Several good guides for doing so:

• https://www.youtube.com/watch?v=IFVYe3riDRA
• https://florianmuller.com/create-a-pihole-high-availability-setup-with-2-pihole-instances-on-proxmox-and-gravity-sync
• https://www.autoptr.top/htmls/i12bretro/0579 (full Raspbian OS)
• https://credibledev.com/install-pihole-on-a-proxmox-ubuntu-container/ (ubuntu container)