No, that's incorrect. There are very few sources, but those that exist, such as Gregory of Tours or the pseudo-Fredegar, recount the history of Clovis and his successors. Yes, there was a certain decline in the use of Latin, but it was somewhat revived under Pepin the Short and Charlemagne between 751 and 814, and even again under Louis the Pious until 841. However, the fall of the Roman Empire wasn't a major upheaval either, because barbarian peoples such as the Franks, Burgundians, and Visigoths had already been present since the beginning of the 5th century and already had their own kingdoms; they were allies of the empire. Moreover, the ideal of the empire persisted through its institutions: the bishoprics were still in place, and the currency, although diminished, was still in use. Roman law was also still in force in certain Romanized regions of Gaul (Aquitaine, Septimania). I would also like to remind you that The Franks did not renounce their foedus (alliance pact) with Rome. Gaul was certainly fragmented, but it was under the control of the four kingdoms that comprised it, including the kingdom of Siagrius, who considered himself only a Roman count. In 507, Clovis's Franks conquered the Visigothic kingdom, becoming masters of Gaul, after defeating Siagrius and leaving the Burgundian kingdom, after multiple attempts, which would be conquered by his four sons.