eBay probably doesn't care what your immigration status is, as the other responders have suggested.
However, eBay is required to report any payments processed into your account if the gross total of the payments is over $600, to the IRS. It's possible that this income could be made available to immigration as well, and if you are violating the terms of your visa by doing work that you are not authorized to do in the USA, then you could face consequences as a result of that (you could be deported). In general, an H1-B visa allows you to do one specific job, for the specific employer who sponsored your visa, and you are not allowed to do any other work.
I would suggest that you need to speak to an immigration lawyer to find out if you would be allowed to sell on eBay, under the terms of your visa. The IRS generally, by default, regards selling on eBay to be gig work, and gig workers are held to the same requirements and standards of any other workers.
The purpose of an H1-B visa is to allow an employer to bring in a foreign worker, who has a post-secondary degree (or an advanced degree may be required in some fields) to fill a position for which the employer is not able to find a qualified US citizen or permanent resident. The H1-B visa allows a qualified candidate to work for that employer only, and only in the position for which their visa was approved.
If the employer who sponsored the visa goes bankrupt, or if the position that the visa was authorized for is not available anymore, then the H1-B visa can be cancelled and the holder would be required to leave the USA.
An H1-B visa is often used as a pathway to permanent residency, and that is allowed and often expected. In that case, you might be better advised to wait a few years. Once you are a permanent resident, then you can do whatever work you want, for anyone.
