Verizon version will not work on AT&T.
Actually it should work, it is just how well it will work or you need it to work. It has the LTE bands 2, 4, and 5 for one.
LTE: FDD1900 (B2), AWS (B4), 850 (B5), 700c (B13)
It also has these GSM and additional roaming bands
GSM/GPRS/EDGE: 1900 MHz (Band II), 1800 MHz (Band III), 850 MHz (Band V), 900 MHz (Band VIII) MHz WCDMA/HSDPA/HSUPA/HSPA+: 2100(Band I), 1900 (Band II), AWS(Band IV), 850 (Band V), 900 (Band VIII) MHz LTE: 1800 (B3), 2600 (B7), 800DD (B20), 700APT(B28A)
You could activate it on AT&T. You just might struggle with it depending on how well it plays with allowing you to add new APN settings. Ideally though you do not want this phone to use for AT&T.
When the one arriving for me finally gets here, I will test my other line for AT&T in it just to make sure and let you all know.