I have a new build with these specs
i3 10100
Asrock B460M Pro4
16GB DDR4
EVGA 500 BQ
 
First time around, one stick of RAM and the ethernet jack on my mobo were dead. So I got them RMA'd and the same exact thing happened with the replacements. Could the PSU have done this? I know they can kill entire components but I've never heard of a situation in where they've killed select parts like a onboard ethernet jack. Thoughts?

It could be quite a few things, like wrong stand offs, no stand offs, long solder joints, bad house grounds, no grounds, forcing wrong plugs in, etc... We would need some more info, like the rest of your build parts, have you done many custom builds or did you buy this one? For it to kill the same parts, twice, in the same way and those parts be low voltage parts like those is very suspicious indeed. If they were high current parts maybe it wouldnt be as weird.