For the time being, you may use the lego-deprecated DNS plugin, which will give you access to all the DNS plugins that Caddy v1 had.
You can see the instructions here:
Nobody is working on one yet, that I know of.
And yes, the libdns interfaces are what we want new DNS plugins to target. Ideally once you have a base implementation, it can be moved to the libdns and caddy-dns organization. You can read this page to learn about how this all works:
Are you aware that Caddy actually comes with a local ACME server from smallstep, built-in?