@Joseph-TP 

hello, yes i can confirm the drive is setup correctly on the router as per the instructions. The drive is visible

and accessible to Time Machine, as well as in the Archer UI, but as per my description, it fails on final setup in Time Machine with the noted message about requiring an existing backup on the drive.

  @punkypj Could you solve it? I am having the same issue.

  @Executek hello, no, no joy 

  @punkypj I'm in the same boat. I've been unable to back up for a few months now, and it makes me a little nervous and unhappy. 

I did have it working once before with the disk formated as FAT, but no matter how I format, I get the error you get. Hope TP-Link will look at this and fix it.

  @Rustopher   @punkypj 

Exact same issue with same result. Frustrating...

Will continue to plug the external drive directly into my MacBook in order to backup. 

TP-Link will point to Apple and Apple will point to TP-Link, all the while the consumer is screwed.

  @ArizonaCalor 

Had also found this thread from Apple Support but didn't get me to the finish line.

https://support.apple.com/en-us/102423

  @ArizonaCalor 

Hi,

Apparently even the devices of the major NAS makers are affected by macOS 26.

Perhaps you can try the following suggestion?

https://www.qnap<dot>com/en-us/how-to/faq/article/why-cant-i-use-time-machine-to-back-up-to-my-qnap-nas-after-updating-to-macos-26-tahoe      (replace <dot> with . )