The patch notes for the April 23 update have been released! Links to the full patch notes are below, but here are some of the major takeaways at a glance.
Surrender is now an option. Stuck in a no-hope match? Your team can now vote to forfeit the game with /surrender or /ff, or by choosing a surrender vote from the options menu.
Matchmaking rules have changed. Instead of triggering a much wider matchmaking range after waiting in queue for at least eight minutes, the range of players you'll be matched against will now scale gradually over time the longer you're in queue. This should result in faster matchmaking in general.
New interface changes have been introduced. These are mostly quality of life changes, such as having your personal healthbar now in bold yellow to help distinguish your own health in teamfights; new, more complex achievements to work towards; and improved merit gains to help you earn and unlock new champions faster. Modifiers now have a basic text search function too, to aid building amplifier sets.
You can view the full patch notes, split into sections, here: