Do newly lined wood burning fireplace chimneys need to be broken in?
The 20+ years became a non-issue with the relining 9 months ago, assuming that was done properly and inspected when finished by somone qualified to inspect it (presumably the installers, in most cases.)

Always a good idea to burn a small wad of newspaper before getting a full fire going to be sure that no birds opted to nest in there these past 9 months, blocking the re-lined flue. If smoke goes up, go ahead and build a fire.

Responding to comment: correct, no "break in" is needed for a stainless steel liner - install it, use it.