It depends on your Lemmy client. I only use Connect, so I can’t tell you where it is in other apps, or if other apps even have it. (Settings -> Filters)

Connect is a simple app and has stabilized quite well over the last few months. Instance, community and word filters have been in the app since I started using it. (Instance filters were implemented long before Lemmy had that as a core feature.)

TBH, Connect was about as close to RIF as I could find at the time and it’s been great. (It’s had its share of bugs, but most are squashed now.)