lxd-tramp.el offers a TRAMP method for LXD containers.
It uses lxc command line tool to login to containers
and list running containers (for completion purpose).
Offers the TRAMP method lxd to access running containers
C-x C-f /lxd:user@container:/path/to/file
where
user is the user that you want to use (optional)
container is the id or name of the container
Thanks to montag451 the author of lxc-tramp.el for suggestions.