Steps to reproduce:

Create a new 3D project
Import TMP Essential Resources (Window > TextMeshPro > Import TMP Essential Resources)
Drag any PNG to the project, set its Texture Type to "Sprite (2D and UI)" and click Apply
From the Project Window, right-click the PNG > Create > TextMeshPro > Sprite Asset
Select the new Sprite Asset, and in Inspector expand "Sprite Character Table"
Click on the entry to edit and change Unicode to "1F6B2"
Make sure value has been set and click "Update Sprite Asset"
In the Hierarchy, right-click > UI (Canvas) > Text - TextMeshPro and select it
Set the text to "x🚲y"
In the Inspector, set Extra Settings > Sprite Asset to the Sprite Asset from step 4
Observe the Game view

Alternative reproduction steps with the project attached:

Actual results: The text shows the OS emoji (bicycle) instead of the sprite

Expected results: The text shows the sprite from its Sprite Asset

Reproducible with versions: 6000.7.0b4, 7000.0.0a7

Not reproducible with versions: 6000.6.5f1, 6000.7.0b3

Tested on (OS): macOS 26.6

Notes:

Not reproducible if the Sprite Asset is assigned before the emoji is first displayed
The OS emoji keeps showing until the Editor is restarted
Built Player shows the Sprite correctly