Can't mount 4TB on RT-AC5300 w EXT4

[Ram]

I recently purchases a Seagate Backup Plus 4TB External USB 3.0 Hard Drive, model STFM4000100. The drive will mount as NTFS, but I cannot get it to mount when formatted as EXT4. I have verified that the drive is using GPT when formated as EXT4. The drive will mount in Ubuntu 17.04. I've also tried formatting with different tools. Disks in Ubuntu, gparted in Ubuntu, and Mini Tools Partition Wizard on Windows 10. I can post logs later, but basically it says "ext4 couldn't mount because of unsupported optional features". I am using the latest Merlin build.
Any ideas?

Also, I am only slightly familiar with the command line for Linux, but if you are clear, I can follow directions well.

 

[ColinTaylor]

but basically it says "ext4 couldn't mount because of unsupported optional features".

I remember seeing this reported here before. Search the forum and I'm sure you'll find the existing discussions.

 

[Jozek]

what you did finally?