Yes, you can that.
--- copied from Adobe FAQ ---
Can I create content with Adobe Firefly and submit it to Adobe Stock?
Firefly generated assets from the commercially released version can be submitted to Adobe Stock if they meet our generative AI submission guidelines and dont contain a watermark.
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newbielink:https://helpx.adobe.com/stock/contributor/help/firefly-faq-for-adobe-stock-contributors.html [nonactive]