Galaxy Tab S2 is psuedo-bricked; will not get past activation process
The issue seems to be an incomplete flashing. The method I did used heimdall to flash the system.img.ext4, cache.img.ext4, hidden.img.ext4, recovery.img, and boot.img files. While this allowed for a bootable system, it did not have Wi-Fi capabilities.

The solution was to get the device's PIT file via heimdall download-pit --output pit.file, then view the PIT via heimdall print-pit --file pit.file | less. You'd then have to go through each entry (my tablet had 42), and flash the file specified to the partition specified. (If the entry has no file name or the file doesn't exist, skip it.)

I do not recall which partition did the trick (I rebooted only after flashing all of them), but Wi-Fi capabilities were brought back.