How to remove iCloud lock on a previously owned iPhone XR?

There isn't an option to bypass that without the owner's assistance. See information in Activation Lock for iPhone and iPad - Apple Support

Since the phone is not usable and the seller isn't helping, you may want to see if eBay buyer protection can help: https://pages.ebay.com/ebay-money-back-guarantee/

You cannot use the phone as others are telling you. Apple will NOT unlock the phone for you and we can't help you unlock the phone. The only person Apple would help is the original buyer of the phone and they would have to present the original purchase receipt, which clearly shows the phones serial number. You don't have that and you aren't the original buyer, so don't expect Apple to do anything for you. Buying used Apple devices, you haven't seen in person from sites like eBay, Marketplace, Offer-up are almost always a waste of one's money.

File a dispute with eBay, but if you can't get your money back, the only thing you can do with the phone is recycle it and learn from this bad buying decision. And read this too --> The All Too Common SAD Reality of Buying … - Apple Community

Mikeycollectsiphones wrote:

Ok I posted it to TikTok and they said that I can ask apple to remove it but I don’t know how because I’m not getting any email

There is a link for removing the activation lock, but it will not help you with a third party device purchased on eBay. The removal of the Activation Lock usually requires the original purchase receipt from Apple or Authorized Apple seller and not one from a third party.

Review the information provided here for the many issues you can encounter when purchasing from a third party:

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

The correct solution is to work with eBay. Also no tips from TikTok will allow you to bypass the Activation Lock.

Return it and get your money back.

If the seller refuses, file a claim under eBay's buyer protection program.

There is no way to bypass that. The fact that you've now been blocked is evidence that the device is almost certainly stolen.

Mikeycollectsiphones wrote:

Ok I posted it to TikTok and they said that I can ask apple to remove it but I don’t know how because I’m not getting any email

Apple won't help if you are not the original owner.

File a claim with eBay and/or your payment used. You bought a brick

Mikeycollectsiphones wrote:

Ok I posted it to TikTok and they said that I can ask apple to remove it but I don’t know how because I’m not getting any email

Nope. Apple isn't going to remove it.

I don’t know what to do with it.

Return the phone for a refund. Get eBay involved if you need to.