If you get a PoE switch many cameras are designed to be run off of the power it can supply over an Ethernet cable. So you just have to run the Ethernet cable (pretty easy).

Also you can get splitters that will break that PoE cable into one Ethernet and a 12v barrel jack for cameras that are not designed to use PoE directly.

I can’t stress enough how much better a direct connection is than wifi, but understand that sometimes it is the only option.

Other benefits include simply unplugging the camera from the switch if it freezes up as this effectively switches it off (this can be done remotely if you have a managed switch.) and obviously higher quality, more stable streams.

Have a look through the frigate documentation before buying a device to run it. It needs some kind of gpu to process the frames for object identification. The most economical one in my opinion is a something intel 8th gen or higher like a hp elite desk mini pc that has a 2.5in sata slot with the igpu and ideally a proper spinning hdd for the recording as it is constantly being written to and an ssd will burn out faster.