I came across the Wikipedia article for the Roman province of Lusitania, and the article states that the province wasn't disestablished until 891. I was wondering if this was a typo, or this province somehow managed to outlast the western empire for a few hundred years.
Link to article: https://en.m.wikipedia.org/wiki/Lusitania
I would assume it's a typo. Even if you assume the Visgothic kingdoms (the kingdom of Toulouse) established under Wallia as a legitimate successor to the Roman state and his successors conquest of the area you run into the problemes of the Muslim conquest and its destruction of the power structure in the area in the 8th century well before the 891 date