Where to download updates for American Carrier phones

As in a phone from an American carrier like AT&T, T-Mobile US etc.

Will focus on the most common phones now (like One M7 & One M8) since those are the ones I tend to see people asking for updates (being outside the US). Instruction and link to a large file is found on the bottom part of the pages linked to.

T-mobile

Sprint

AT&T

Verizon

Updates comes only as OTA via/from Verizon