I've been watching Paper Girls on Prime and if you're looking for something to fill the gap until Stranger Things returns, it definitely will. I watched Outer Range and Tales from The Loop and I wasn't impressed with either.
Just to add to this, Citadel on Prime has been great so far too.
I'm currently watching The Sandman on Netflix and it's been excellent so far. Though considering that it's a fantasy series on Netflix, I'm not hopeful it's going to get a second season. I also watched 1899 and you can add my voice to the chorus who are disappointed that it was cancelled after one season, I hope that another streaming service picks it up or they do a movie to wrap it up.
Just to add to this, if you watch 1899, don't skip the opening sequence! Not only is is really cool, you'll also realize that it telegraphed the plot twist when you watch the final episode.