If you can't find your favorite addon, try reaching out to the author on WoWInterface or CurseForge to see if there will be a new version.
Of course, not every addon from either Retail or the Vanilla version of the game has been ported to Classic as with any fan made project some are no longer maintained or their authors may not be interested in Classic. Whether you're looking for UI improvements, help managing your inventory, or where to find the next quest, there seems to be something for everyone, and so we've updated our list of recommended addons for Classic WoW in the hope that you might like them too! Classic has been out for a nearly a week now, and we've had a chance to play with several new and returning addons being maintained by devoted fans.