Hello there, so we are encountering a strange issue with some characters' portraits.

Here's the one with the most visible issue, as you can see around the mouth there's a line and that's basically on the edge between colored and transparent pixels.

During our tests we tried exporting with different scales, the next screenshots are with export scale 1 (and the texture is 4096x2048)
I'll try to keep things sorted.

First of all we are using Unity 2023.2.20f1 in URP and Spine 4.2

In Unity with Premultiply Alpha

The next one uses a previous version of the model that was export with scale 1 (and the texture is 2048x1024)

it can be seen that the issue is a little bit more visible.

At first we thought it could be some problem with premultiply alpha VS straight alpha, so we checked everything in Unity but it seems things are properly set.

I'll attach more screenshots.

1) color is set to gamma

2) texture is not using sRGB (nor Mipmaps), we also tried to remove the Bilinear Filter Mode (it did not have any effect on this)

3) we are using the standard material(s) (it happens both with SkeletonAnimation and SkeletonGraphic) and the Straight Alpha Texture is disabled

4) the atlas is showing pma:true

5) the packages are installed via UPM

What we see in Spine

We tried to see if the issue could be on the Spine side, but to no avail.

1) the source graphics when in straight alpha does not have any strange smudge (here's a gif our animator took)

(if it's rendered too quickly you can see it here )

2) here's a screen on how it appears on Spine, the smudges are definitely not there

3) here's the export settings

We thought to try to enable Bleed (as it was mentioned somewhere else to try) but it seems we can only select either Premultiply alpha OR Bleed.

In Unity With Straight Alpha

We also tried to export with straight alpha (and see everything in order to use the straight alpha texture), and compare the results but it seems just worse.

this was exported with the straight alpha option (as can be seen in the atlas.txt)

Do you have any pointers on what could be the cause?

Let me know if you need some more info / if I missed something,