Your device is not supported by /e/OS,
It was supported by LineageOS but actually not maintened,
The Canadian AT&T Samsung Galaxy s5 (SGH-I747M) code name : d2att
https://wiki.lineageos.org/devices/d2att
you can flash the custom recovery,
TWRP for the d2att (custom recovery for your device)
UNOFFICIAL_LineageOS_14.1_d2att.zip (android 7 nougat image for the ROM of your device without Samsung stuff)
([HOWTO] Install /e/ on a Samsung smartphone with Windows easily) (or another custom image ROM)
If you find resources and knowledge, it could may be possible to build an unofficial /e/OS image for the ROM of your device.
(https://github.com/LineageOS/lineage_wiki/blob/master/_data/devices/d2att.yml)