Here’s their documentation. The tip suggests it may have been harder in the past but it doesn’t seem too bad now. Hopefully this is configurable in Xen Orchestra in the future.

https://docs.xcp-ng.org/compute/#️-usb-passthrough

Consider checking out XCP-ng. I’ve been testing it for a few days and I’m really enjoying it. Seems less complicated and more flexible than Proxmox but admittedly I’m still learning and haven’t even tried multiple servers yet. I would suggest watching some YouTube videos first. Good luck!

You can use HACS in Docker. I definitely had that working in Docker before I moved to Home Assistant OS on a dedicated machine. You’re right about add-ons though, maybe you had the two confused?