Recently came across FluffyChat (https://fluffy.chat/), which works on matrix and has funny stickers and emojis ;)

And for desktop apps, Cinny has custom emoji/sticker support. Would be nice if they played better with Element though.

I've been using fluffychat for over a year. It's a nice interface and the client I used to convince less technical friends and family to give Matrix a try. Unfortunately major functionality like being able to send images becomes broken for long periods of time https://github.com/krille-chan/fluffychat/issues/2497