Weird lines & fading under TMP_Text (UI) in Unity 6 (original) (raw)

Describe the bug
After updating to Unity 6, weird fading & lines started to appear beneath UI-texts that are rendered inside of a SoftMask.
Updated SoftMask from 1.0.2 to 3.2.0, fixed assets & updated/registered shaders, but this does not seem to have resolved the issue.

Texts use 'TextMeshPro/Mobile/Distance Field Overlay' for their shader, which gets replaced with 'Hidden/TextMeshPro/Mobile/Distance Field (SoftMaskable)' in the mask. Disabling the Mask reverts the shader and makes the text sharp again.

Enabling "Extra Padding" on the TMP-Text (UI) seems to move the line downwards, but does not remove it.

Setup
Texts are inside a ScrollRect.
Softmask is on the Viewport of the ScrollRect, intending to fade out the contents on the edges (horizontally).
Texts are nested inside content inside of the ScrollRect. They use the 'TMP/Mobile/Distance Field Overlay'-shader, which gets replaced with 'Hidden/TextMeshPro/Mobile/Distance Field (SoftMaskable)'.

Expected behavior
Text inside of mask is sharp and legible as normal.

Screenshots

Mask Enabled:

Mask Disabled:

Extra Padding:

Environment (please complete the following information):

• Version 3.2.0 (Updated from 1.0.2)
• Platform: All (WebGL/Android/Editor)
• Unity version: 6000.0.35f1 - Unity UI 2.0.0 (apparently TMP is now part of Unity UI?)
• Build options: N.A.