iPhone XS and iPhone 8 stuck in iPhone unavailable without option to connect to iTunes

What you bought was a bunch of bricks. Even if you did know the password, you are most likely going to run into Activation Lock. Chances are you purchased stolen phones since the seller disappeared, contact eBay and see if you can get your money back.

Activation lock is a security protocol that can't be bypassed. Only the person it is locked to can unlock it.

If you bought this from someone and it came locked, try to get your money back, you will never be able to use the phone.

If your phone is Activation Locked - How to remove Activation Lock -

How to remove Activation Lock - Apple Support

The All Too Common SAD Reality of Buying a used phone -

The All Too Common SAD Reality of Buying … - Apple Community

If you forgot the passcode on your iPhone, or your iPhone is disabled or unavailable -

Click on the link for instructions on how to reset your passcode without a computer if you have iOS 15.2 or higher.

If you see a iPhone, iPad, or Apple Vision Pro unavailable message or Security Lockout screen - Apple Support

Click on the link for instructions on how to reset your passcode using a computer.

If you forgot your iPhone passcode or your iPhone is disabled - Apple Support

The phones that you bought were not properly erased for resale. They should have opened up to the "hello" screen. Even then, no guarantees.

The seller(s) should have followed these instructions.........What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support........but they didn't.

The sellers can't help you and the carriers can't either. Notify eBay that you want to return the phones for a refund.

The All Too Common SAD Reality of Buying … - Apple Community

GabeTehGamehAlt wrote:

I don’t know what to do with them

Toss them in the electronics recycling bin at your local Apple Store or other electronics retailer.

And take this as a lesson in buying electronics from untrusted sources.