I realize this is an old post, but wanted to give a brief answer to your question and provide a link to an already made docker file for others who land here after a good search.
Does it make sense to create a samba server as a domain controller in a container and which is visible on the host’s network?
What advantage does it have vs install Samba directly in the host? What i performance does it have? Is it suitable for a small LAN (3 more or less computers)?
It has all the benefits of being in a container… Many containers can run on a single host server. The containers don’t generally interfere with each other. If something goes wrong with the container, it is quick to re-create another one.
Yes, it is suitable for LANs with even 100x that many computers.
Now, to make things easy: here is the link to an Alpine Samba Domain Controller docker file.