This fixes the broken rotation on the Acer Spin 1 I recently bought (exact model is SP111-34N-P4BZ).
It is possible that all of the SP111 models would use the same matrix, but to be on the safe side, I added a new entry.
sensor:modalias:acpi:BOSC0200*:dmi:*svn*Acer*:*pn*Spin*SP111-33*
ACCEL_MOUNT_MATRIX=0, 1, 0; 1, 0, 0; 0, 0, 1
+sensor:modalias:acpi:BOSC0200*:dmi:*svnAcer*:*pnSpinSP111-34*
+ ACCEL_MOUNT_MATRIX=0, 1, 0; 1, 0, 0; 0, 0, 1
+
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