JPEG XL also supports layers. It only supports normal blending (and a few other blend modes but certainly not all of the blend modes of Photoshop) and it doesn't support layer effects, but for the basic use cases of layered images, it can be used to store an image (lossy or lossless) with the layers preserved, no flattening/merging needed. Layer names can be preserved too.
Of course it's not a replacement for PSD — there are plenty of things it doesn't support, like text layers etc. But it could
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