In UEFN, you need to use the Cinematic Sequence Device to play Level Sequencer data.
This Cinematic Sequence Device includes an Instigator Only setting that makes the Level Sequence playback visible only to the Agent who triggered it.
In this article, we summarize the results of our tests—broken down by pattern—on how it appears to Agents who are not included under Instigator Only.
https://dev.epicgames.com/community/learning/tutorials/WVWD/fortnite-cinematic-sequence-device-instigator-only-behavior-multiplayer-compatible