Here is just a little theory about AoS S6 which is pure speculation, with a little inspiration from this post
With some clues from the Spiderman Far From Home trailer, I think the Agents of SHIELD have jumped into another multiverse.
In the trailer, Nick Fury told spiderman that the snap ripped some holes in their dimension, so it is very possible that the Decimation snap is the snap nick fury was referring to if this theory is correct. Because the snap happened when the agents of SHIELD was tampering with time (changing timelines), it is very possible that they have traveled to another very similar multiverse without even noticing.
So it is very possible that they have gone in another timeline without noticing. Here is something that is even more interesting but is still just a theory without any points to support. Sarge's team maybe using the ray gun to track down the people/things that are obviously from another multiverse, like Deke and those flying creature in the latest episode, as he and the creatures are from another timeline. But because the agents' travelling across the multiverse was really subtle, the ray gun can't even detect them in the wrong multiverse.
With the post by JohnTitor, I think it is Sarge's team which is the key for the agents to travel back to their own multiverse/timeline
This theory is pure speculation, so take it as a grain of salt.
P.S. I actually wanted to post this after the next episode comes out as it seems to have a lot of answers to our question, but I just couldn't wait...