We set up a bridge between the Lemmy.world General Matrix room and the Public-1 channel on the Lemmy World discord server yesterday. It’s not perfect as emoji reactions aren’t visible and some minor things like how it handles edited messages but other than that it seems to be working well.
Now people on both chat clients can interact with eachother!
I use the chat that is available in Thunderbird, my email client. It can connect to various types of chat (I dont remember them all) like Matrix.