@AmazingMiki 

Just realized that indeed it is the power:

What should I do if TP-Link router cannot detect my USB flash drive or hard drive

"""

4. Additional Power Adapter

Usually our router can power up the hard drive, but for some, additional power supply may be required.

If your hard drive needs a power supply more than 500mA, but it does not have an additional power adapter, then this hard drive can not work properly with our routers since ours only provide 500mA power supply on the USB port.

"""

Indeed my HD requires 900mA , which is 400mA above what the router provides according to that link.

I should find some way to provide the HD with an additional power supply, no idea how to google that yet.

Update:

I found some usbc hub laying around that has a usbc power socket,

so I connected a phone charger to it's power socket,

the HD to a usbA socket

and then I connected the hub to the router

only after a restart to the router it was able to recognize the HD, but it did

unfortunately 80% of the content (folders and files) is unrecognized by the router - I only see a few folders but the rest are missing

its a single partition of 2 TB if that matters anything.

Uodate2:

Speeds are super slow, sometimes it just crashes (meaning the 1 second ago available share becomes unavailable anymore) even the web ui freezes, as soon as I disconnect the HD the router works as normal again

@Kevin_Z 

I think the phone charger gave it too much power, made the router unresponsive unstable.

Accessed via smb and ftp, it's ntfs. Saw only 3 folders when it had 20 in fact.

I changed the power supply to be the other secondary usb3 port of the router, it gave it just the right amount and now it's working perfectly fast and stable through smb and ftp and I can see there 100% of the original content no issues.

Only issues is media share via DLNA, I am able to view only 3 directories and no contents, non of them have media in them and those that do contain audio video and pictures are not one of the 3 I am able to browse using DLNA.

Browsing using LG Smart TV.

@AmazingMiki 

DLNA was resolved as well eventually.

Originally, when I connected the bad power supply and only 3 folders were visible in smb,

I think that's exactly when DLNA saved that kind of data

so when the correct power supply was connected and smb was fixed - DLNA was not refreshed and the old bad data remained.

not 100% sure which of those voodoo actions forced DLNA to refresh, because I did them before to no effect (a shame there isn't a force-refresh DLNA button in the ui)

but this is what I did:

toggle off some random folder from being shared under the partition (recycle bin)

toggle off Media Share (DLNA)

toggle on Media Share

and then it re-populated 100% of the partition's contents, finally!

I have no further issues with the AX6000 usb storage anymore, a bit of a shame I had to voodoo my way around to activate hidden features instead of just clicking them directly.

I hope these UX problems are fixed before the next meaningful versions for future clients. but right now that's no longer my problem : ) hope it remains like that.