Diamonds in Minecraft remain one of the most valuable resources in the game, and this hasn't changed in the 1.21 update. They're a core crafting component of various blocks and items, including the creation of high-quality tools/weapons/armor, and even the ability to duplicate smithing templates. Because of this, it's no surprise that players want to find diamonds early and often.
Acquiring diamonds in Minecraft 1.21 is the same as it has been in previous updates. Still, it doesn't hurt to examine how you can find diamonds in the Minecraft Tricky Trials update to meet your crafting needs.
Ways to find diamonds in Minecraft's 1.21 update
Looting generated structures
Despite there being better methods for collecting diamonds in Minecraft 1.21 when it comes to volume, looting generated structures across the Overworld, Nether, and End is still a great way to supplement your diamond supply, especially because some structures tend to offer a few more diamonds than others or at a higher likelihood.
Structures where diamonds can be looted
Mining
When it comes to getting diamonds in Minecraft, mining is still one of the most reliable ways to do so, but you'll want to know how diamond ore is generated for optimal diamond mining. Specifically, the lower your elevation, the more concentrated you can find "blobs" of multiple diamond ore blocks, and concentration is particularly high at around Y=-59.
You can certainly mine deeper toward Y=-63 and still find diamond ore, but the ore blocks tend to occupy space more often with bedrock blocks at that point, so mining slightly above at Y=-59 proves to be incredibly effective.
Trading with other players
Although this doesn't really apply to those who are enjoying the game solo, another solid way to get diamonds in Minecraft 1.21 is to barter for them with other players or shops/NPCs set up on multiplayer servers. You'll need some items or blocks of equal value for the trade unless your fellow players are feeling charitable, but bartering remains a perfectly reasonable option in multiplayer.
Unfortunately, single-player fans won't have access to this same luxury, at least not in the vanilla game. While certain villagers are willing to purchase diamonds, they don't offer raw diamonds or diamond ore as transactions. You can get diamond tools and gear from villagers, but these items can't be smelted in a furnace back down into diamonds.