https://www.amazon.com/gp/product/B0974TK3KD/
PoE operates at a pretty high voltage (almost half of line voltage!) and Waveshare products aren't UL listed.
No, it operates at ELV (extra-low voltage): https://en.wikipedia.org/wiki/Extra-low_voltage
The whole point of PoE, 48V PD USB-C, and similar tech is that they don't need to be UL listed. PoE is also electronically current limited unlike mains power so you can't pull 200A to start a motor nor can you start fires without a lot of effort. That's assuming you use a real PoE switch that negotiates power levels, not cheap passive injectors.
Anyway that hat has some bad reviews claiming DoA, missing components, and dead Pis. Why not get the official hat? https://www.raspberrypi.com/products/poe-hat/
Or there are ways to cheap out on a PoE device that may work in some cases but don't fully and properly implement the standard.
The standard is widely used in VoIP phones, wireless access points, security cameras, and all sorts of other networked devices that get installed in places that may not have nearby power outlets or where a single wire solution is beneficial.
Personally I have three Pis that have been on PoE their entire lives and have had no problem, but I used a name brand PoE hat (the Waveshare hat with the OLED display) and am powering them from a mainstream PoE switch. If you're using some random AliExpress hat with janky injectors you get what you pay for.
> I wouldn't trust the hat or whatever you call it for Mac Mini.
Almost any large commercial building has had hardware running on PoE that costs more than the average Mac Mini for years. Most PTZ cameras for example, high-end directional wireless bridges, even some nicer wireless access points.