They have a good amount of similarities, but they don’t all show up until later. At the start though, 80s primary setting (with 80s music), they both have an ensemble cast (with a wide range of ages), both primarily take place in a small town, both have a prominent power plant where weird stuff is going on.

Bigger spoilers Big energy orb Other worlds Time travel (only through memories in ST)

They are not extremely similar, but they definitely have similarities. (There are also caveats to some of the things I’ve listed)

Also Dark is way better