system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] Could there be more than two Sith Lords operating at the same time, unaware of each other?

Darth Bane's "rule of 2" means there is only a master and an apprentice Sith at any one time. And we can assume that Darth Sidious can trace his Sith lineage all the way back to Bane. So, there should be a master who holds the power, and an apprentice who desires it. This also leads to Apprentices who will groom people to be their Apprentice once they kill their master, and Masters always on the lookout for a better apprentice.

But in the expanded universe/Star Wars legends lore, we see that there are Sith artifacts, Sith Holocrons, Sith force ghosts, and other Dark side memorabilia that will lead a force sensitive down the path to becoming a Sith.   And we know that Sidious was able to completely hide his Dark Side connections from the most powerful Jedi. 
So, is it possible, maybe even probable, that a completely independent Sith lord and apprentice could be in some corner of the Galaxy, unaware that they were violating the Rule of 2, hiding themselves from the "goodness" of the Jedi and the Republic?
gpt
Simply having Sith artifacts and holocrons in your possession does not make one a Sith.

Could there have been other Sith around after Bane and before Palpatine? Maybe, but very unlikely. Legends even had a whole Lost Tribe of Sith that were separated from the rest before the Rule of Two was even thought of.

But canonically, the Sith are dead and gone after Endor. There are no others, the Sith died out with Sidious and Vader.