I'd much prefer this be built into lemmy itself. You can block users and communities already in /settings. A keyword block would be a nice addition to that. Advanced blocks where you could block certain keywords (or domains) in certain communities by certain users (or any subset of those) would be amazing.

Rather than per client, I'd prefer this on the server side.

Me too. These people are abso-fucking-lutely obsessed with Elon. Weirdly this has made me sympathise for Elon. I didn't have any opinions about him before

I'd filter Jerbora, Jeroba for starters