@disillusionhk,
First off the tracking info displayed by ebay, actually is provided by a 3rd party, not directly from the carrier itself. You can get more up to date info by going directly to a carrier's tracking site, in this case do a search for UPS tracking then copy and enter your tracking number there.
"Another weird part is that on the item's product page it shows that the seller (under the "Shipping:") is located in New Jersey, United States but the UPS tracking shows the item was shipped from California, United States".
Many high volume sellers who give an item location in N.J. are actually located in China, and may ship from there. If a seller gives an item location of N.J, United States, that is an in appropriate location, often used by chinese sellers. It should give a City and State Ex: New Brunswick, New Jersey.
"Should I file a claim immediately through UPS? Can I contact eBay directly somehow? Should I contact the seller?"
UPS will not give you the info you need, they will tell you they cannot because you are not the Sender. There is no sense trying to contact the seller/scammer, they will say it was delivered if they bother to answer at all. There is really no way to Contact ebay about the issue that will help at this point. However, I responded to a topic about the fake tracking info yesterday (link below) that explains what has to be done, in order to get a refund.
Unfortunately, the link you posted was to a topic originally posted in 2021 as the fake tracking scam was gaining popularity. There have been many newer ones that have been posted since, with responses that tell you how to go about getting a refund. Such as the one below where I explained what has to be done to get a refund. READ THE REPLY. Your best bet would be to go the social media route.
https://community.ebay.com/t5/Ask-a-Mentor/Seller-says-I-receive-a-package-that-I-never-received-eBa...
In the future, You need to check the feedback profile page of any seller you intend to buy from, before buying. You do that by clicking on the number in ( ) to the right of their username, yours is currently (11 ) On the page that opens, you can see a seller's country of registry, and there is a box with the numbers of the 3 types of feedback they have received. You can click on the numbers of neutral and negatives they have received, to read only those comments. Never go by a seller's feedback percentage alone. If a high volume seller has a feedback percentage below 98.6% do not buy from them, especially if you see they are registered in China or have feedback saying some items shipped from there or from a different location.
"THERE IS NO SUCH THING AS FOOLPROOF, BECAUSE FOOLS ARE SO DARNED INGENIOUS!" (unknown)
