Will the TL-SG1008P power a passive-PoE device?

Do not assume so. The TL-SG1008P provides standards-based IEEE 802.3af/at PoE, which is different from proprietary or fixed-voltage passive PoE arrangements.

If a device specifically requires passive PoE, check its power specification and use the correct power source rather than treating every form of power-over-Ethernet cabling as interchangeable.