Yes, it is possible to use the SDM_IO9 pin for the PWRMGT_ALERT signal in Intel® Stratix® 10 devices, even though the Intel® Stratix® 10 Device Family Pin Connection Guidelines document does not list this pin as one of the supported locations for PWRMGT_ALERT. Selection of this pin is already permitted in the Intel Quartus® Prime Pro software
The Intel Stratix 10 Device Family Pin Connection Guidelines will be updated to include this information in a future release.