On the website, the buttons beside a message are now Add reaction, Continue in thread and ⋯. ⋯ opens the message's menu: the reactions, Continue in thread, Copy text and Delete message, which is no longer a button beside the message. Right-click a message for the same menu.
On a phone or tablet, tap or hold a message on the website to open its menu, as in the mobile app. Double-tap someone else's message, on the website or in the app, to add 👍, and double-tap again to remove it.
The mobile app no longer offers reactions on your own messages, which could not be saved.