If you're here then I'm going to assume you already know about B.A.T.M.A.N and Netplan, and probably also about ifupdown (or at least /etc/network/interfaces
).
Bad news: Netplan cannot currently (2023) set up batman-adv interfaces. Simply no support for it. This suggests that, in order to have batman-adv interfaces, you have to uninstall Netplan and switch back to ifupdown.
Good news: Netplan uses systemd-networkd under the hood, and it does have support. You'll bypass the Netplan configurations and write your own, but it's not too hard. So you can keep Netplan installed and managing your non-batman interfaces.