We have shown gnosticism was alive and well into the 4th century, what information is there that it died off? It didn't die off anywhere else.
Is that just an assumption on your part or do you have something at hand to demonstrate that Gnosticism (in whatever form) lingered past the 4th century?
But in the 5th century the Visigoths became the dominant authority in the region, and while centered at Toulouse, controlled much of the Iberian as well as southern Gaul. Alaric II as King of the Visigoths was an Arian, but tolerant of both Catholics and Gnostics.
Tolerant of Catholics, yes. But do you have anything at hand to demonstrate the idea that Alaric was tolerant of Gnostics? Or that there were Gnostics in significant numbers in the Visigoth's kingdom to tolerate?
after 508 most of the Gallic holdings were lost to the Franks (Merovingians), and although Clovis did convert to Catholicism, the Merovingians did allow Gnosticism and Arianism to flourish.
Highly doubtful. What's your source for that statement?
Even under the later Carolingians the Gnostic and Arian sects continued.
As far as I can tell, there is no record of an attempt to wipe out Gnosticism in the area until 1022.
The incident you're referring to occurred at Orléans, and three years later at Liège and Arras. Northern cities. I had thought we were discussing the survival of Gnostic sects in the south of France. By the way, the accused in all three cases were Catholic monks and priests "infected" by a heretic monk from Lombardy named Gundulf, whose "heresy" was only nominally comparable to that which sprung up in Albi a century and a half later. Public burning of the victims was carried out Orléans, but those of Liège and Arras recanted and were spared. These weren't incidents of popular uprising over a latent belief system, these incidents occurred within the church itself.
There can be little doubt that several forms of Gnosticism existed in the area well into the Catholic era. All of these having similarities with each other, and they all seemed to evolve from either Manichaeism or Valentinian Gnosticism. As a matter of fact, the word Katharoi in a similar form was the name of a sect that the father of Mani had belonged to.
"Katharoi" was a name applied to several heretical sects whose origins were not necessarily common or related. And given that the "Catholic era" began in the late 4th century, how long does "well into" mean and what do you have to back it up with?
So when HBHG mentioned that the Gnostic Cathars "seemed to represent the flowering of something already rooted in French soil for centuries", they could well have been correct.
I'm still waiting to see some evidence to support that idea - that it was "rooted" in France and survived below the radar until the 12th century.