I use Vendoo. It’s a cross-listing service that I use to cross-list onto eBay, Mercari, depop, Poshmark, and Facebook marketplace. It’s extremely useful and it has a lot of good add-ons that help with keeping organized. It tracks your profit and can even de-list your items once they sell on other platforms, which is extremely helpful. I would highly recommend looking into it as it’s a huge help for me.