If the Series 5 could work with any Qi charger, I imagine they would have called it out during the keynote. And since the hardware is mostly the same as the Series 4, it's pretty safe to say, IMO, that the Series 5 will only work with specific chargers cleared by Apple just like the Series 4.
Apple uses a "Apple modified" version of Qi on the watch because Qi does not meet their wattage requirements. So in Apple's version of the story, Qi would be a downgrade.
Now that the Apple Watch S5 is out, has anyone able to verify that the new Apple Watch finally works with regular Qi chargers? (this is a must have feature for me in order to upgrade from my S3).
Nope. Only works with the apple chargers that come with the watch. The apple supported qi chargers (mophie and Belkin) that charge iPhones at the 7 watts do not work.
Only ones that will work are chargers designed for the apple watch..I have a SS S3 and just upgraded to a SS S5