I have a Canon T7i and I need to wirelessly trigger unmounted 430EX III-RT. Can the camera do it on its own or what do I need to make it happen? Thank you so much!
Yes, your camera can control your flash using optical communication. See page 217 and following of the Camera manual. You of course have to set the flash to "optical slave" mode ("lightning" icon) and make sure it is on the same channel as the camera.
Tip: in the camera flash settings, you can set the lighting ratio between the camera and the external flash, in general you want to dim the camera flash a bit.
The existing answer is true only for mid-range cameras. Low-end and high-end cameras do not have the "easy wireless flash" functionality. High-end cameras do not have it, because they lack the integrated flash.
For those wondering the same for low-end and high-end cameras, to trigger 430EX III-RT, you can use either Canon ST-E2 infrared trigger or Canon ST-E3-RT radio trigger (or 600EX-RT as radio master, but that's an expensive route).
Which one of these two to use depends on whether you need non line of sight triggering in outdoor conditions (then ST-E3-RT is the only option), and whether you can find a used ST-E2 from a second-hand market (they are usually very cheap, $50 or so). If one has to buy ST-E2 new, then it's nearly as expensive as ST-E3-RT. I probably wouldn't buy ST-E2 new unless I wanted to trigger second-hand flashes lacking the RT feature. However, if buying flashes second-hand, one can perfectly well buy the ST-E2 second-hand too.
Also, Canon's more expensive flashes (600EX-RT) can work as a radio master to control 430EX III-RT radio slaves.
Additionally, do note the ST-E2 uses peculiar 2CR5 batteries.
Can Canon T7i trigger an unmounted 430EX III-RT?
Yes. The built-in popup flash on the EOS Rebel T7i/800D can act as a master flash to control an off camera 430EX III-RT flash.
The camera side of things is covered on pages 220 and following of the EOS Rebel T7i/800D Instruction Manual.
The flash side of this method is covered on pages 71 and following of the Speedlite 430EX III-RT/Speedlite 430 EX III Instruction Manual.
Please note that this uses the older optical external flash control method, rather than the newer RT radio external flash control method. Other than the need for an additional radio transmitter attached to the camera, radio communication is superior to optical communication in just about every other way.