The syncserver is the trivial part. The less-well-documented web of 5-8 fxa-yxzablgt services (FX-Account-server) that you need to also run is the issue. The docker github readme warns against anything but "messing around" type usage, and the last update there was 7 years ago.
( fxa-content-server
fxa-profile-server
fxa-auth-server
fxa-oauth-server
browserid-verifier
fxa-auth-db-mysql )