System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce GTX 1080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 460.79

Blender Version
Broken: version: 2.91.0, branch: master (modified), commit date: 2020-11-25 11:06, hash: rBb50598bc78c7
Worked: (newest version of Blender that worked as expected)

Short description of error
When performing undo during sculpting in Blender 2.91, the undo undoes last changed UI parameter alongside last stroke when pressing undo shortcut (Ctrl+Z). In this particular illustrated instance, color space of a newly loaded image texture. But in general, it undoes almost anything made prior to the first stroke, such as brush size, etc...

Exact steps for others to reproduce the error

1. Open the attached .blend file:
   Ground_Close_V01.zip11 MBDownload
2. Enter sculpt mode on the selected object.
3. Load another texture to be used as a brush texture, as seen in the video
4. The texture color space will incorrectly revert to sRGB, change it back to linear.
5. Make a sculpt brush stroke on the mesh
6. Undo the stroke

Result: Undo undoes the stroke, but color space change at the same time.
Expected: Undo undoes only the brush stroke.