Is there a way to ignore all content from specific instances?
There's content coming from some specific instances that I'm not particularly interested in. When I'm browsing content outside of my local instance, can I prevent all content from one (or more) specific instance(s) from being displayed?
From the web interface it's pretty easy. You can either go to the community page and click the "Block Community" button in the sidebar, or you can go to your Settings
or you can go to Settings -> Blocks and manually search for the community to block there
If you're using a mobile app it will depend on how the app has implemented it, but generally it involves going to the community page and tapping the hamburger/meatball (3 lines/3 dots) menu and selecting Block from there (might have to view the Sidebar, then block from there).
It seems not all of the apps have implemented blocking yet. I can't seem to find a way to do it in wefwef, but Mlem and Memmy have it, for example.
Currently only way to block a entire instance is defedarting in instance to instance Level. So you would either need to convince your instance admin to defederate or host your own. But I don't see a reason why this wouldn't be possible in future. It can even probably be implemented by a third party client without any changes to Lemmy api
I don't know enough about how Lemmy works on the back end - but maybe something like a PiHole blocking all traffic to the domains of instances you don't like. I'm unsure if the device requests that data directly from the other instance or if the instance you're connected to retrieves that data and sends it as it's own.