Cloud computing is a well-established technology that has been already widely used due to its extensive benefits. However, with many systems still relying on traditional architectures, existing literature has focused on aiding in their migration process. Nonetheless, comprehensive studies integrating both white and grey literature to assist professionals and researchers in understanding strategies for migrating legacy systems to the cloud are lacking. We addressed this gap by identifying challenges and opportunities related to migrating from on-premises to a cloud environment. Following this, we first conducted a systematic literature mapping to summarize the knowledge regarding migrating legacy systems to the cloud. Then, we performed an exploratory analysis of discussions on Stack Overflow and other question-and-answer (Q&A) communities within the Stack Exchange network to gather professionals’ perspectives on this topic and compare these perspectives with the knowledge found in the literature. Finally, we developed a Proof-of-Concept (PoC) of a decision support tool using a Large Language Model (LLM) that provides targeted responses to questions about migrating legacy systems to the cloud, enhanced by the Retrieval-Augmented Generation (RAG) method.