If you can wait a bit you can get sync for lemmy.

Pacman!

You could group them and look at everything “outdoors” related from multiple communities in a single feed.

I hope that with future versions of lemmy they can create “lists” that people can subscribe to that will do this.

or at least let you add communities to your own lists that do that.

I am on lemmy.world and can see it

In order to subscribe to another instances communities you still need to be on your community. For example if you click a link that takes you to https://lemmy.ml/c/announcements it will take you to lemmy.ml where you are not logged in, however if you click on the community name is a post that shows up in your feed, you will browse that community FROM lemmy.world.

You could also browse like this:

https://lemmy.world/c/[email protected]

This is unfortunate. But not surprising. Hopefully they still contribute to many other open source projects

Not at this point. Unless you run your own instance.