Joining random RBG's

Hey good day.

I played this game for some years but I’m a little bit out of touch with how people communicate as of today.
Yesterday I had some fun random rbg’s while grouping up with strangers.
I don’t know how people start these. I can’t just wait till people ask right? Are people communicating for these groups normally somewhere?

I’m now waiting till I find some random in LFG but I want to seek these groups out myself. So any tips are appreciated. Just downloaded discord but I’m a little noob in that regard, added some channels I could find online but became not very wiser from that.

Thanks in advance.