I just set up obs as a virtual webcam and do that. It doesn’t do audio but most of the time that doesn’t matter. I find it has a much smaller performance hit that screen sharing via Discord itself.
I love this. My steam deck has been a life saver and all these changes also let’s me game on my desktop.
I was playing Hunt: Showdown without issue this morning.
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/announcements@lemmy.ml