A bind mount kind of shares a directory on the host with the container. To do it, unless something’s changed in the UI that I don’t remember, you have to edit the LXC config file and add something like:
mp0: /path/on/host,mp=/path/in/container
I usually make a sharing dataset and use that as the target.
I have a couple older Minis in my Proxmox cluster. One’s a 2012 model and the other is a 2018. They both run great (and the 2018’s got 64GB of RAM and 10Gb Ethernet). I’m not sure I’d go looking for them for a homeland, but they’re great to repurpose.