gcotterl wrote:
The panel is made by Decorative Panels International (DPI)
The label says: 1/8" embossed tileboard
Model #627 - Design: "Toned White". (The face has shiny white
squares; the back is tempered hardboard)

The "application instructions" say the (un-installed) panel can be cut
with a fine-toothed handsaw. But how do I cut the panel that's
already stuck on the wall?

Another job for the Harbor Freight Multifunction Tool? (or similar)

Be sure you wear saftey glasses and do not operate tool when wet or under
the influence of alcohol (you, not the tool).