As a long time seller/buyer I’ve developed a set of heuristics around eBay (most of them obvious - avoid non US based accounts, descriptions where the photos are clearly not the actual item itself, etc) and I’ve only had one or two bad surprises in over 10 years. Both times customer support came through.
A buyer screwed me out of 5 drone (DJI Mavic 2) batteries and $700. Two weeks after getting the drone, “none of the batteries work”. Really? All five? I was skeptical, but said I’d do a partial refund if he’d commit in writing that the partial refund was contingent on him returning the batteries so I could repair, or replace (at least two were still in warranty, if there was ever even a problem). At no point did he show any actual evidence of battery issues (DJI Go battery diagnostics, etc.), just "it's not showing anything".
He sent a message agreeing, via eBay messages with the text I'd sent him, even with "should I not do this, I understand that seller will dispute the transaction".
Not even an hour later he sent another message “USPS won’t ship damaged batteries so I am not returning them”.
I went to eBay with all this, and his agreement. eBay said he could keep the $700. And the five batteries.
That’s what makes me weary that there’s any way you can truly avoid Amazon. For many sellers it’s just easier to outsource their warehousing and fulfillment operations to FBA and use Amazon’s warehouse as a 3PL (third party logistics), and I wouldn’t be surprised if <random eBay/Shopify seller> used Amazon for fulfillment purposes.