Ruined portals generate floating in rivers instead of underwater
Ruined portals generate floating on water in any biome that is not an ocean instead of being submerged. I could not find a great example of this in 21w40a, but they can generate without even touching any solid blocks in wide rivers.
Examples:
seed: -5122813796493059606
261 64 -14337
386 68 -22726
381 65 -31362
165 76 -36399
374 68 -62029