Yes it is.
https://summit.news/2019/04/15/notre-dame-cathedral-in-paris-on-fire-worker-claims-it-was-deliberately-started/
In what case would somebody who works in NotreDame, 'cathedral staff' , most likely know it was likely intentionally set? What reasons would they have? This seems more likely with observations leading up to the fire as opposed to knowing something about a spontaneous 'radical Islam' act of arson. If it was a spontaneous attack, why would we only be hearing this from staff but not elsewhere?
I am guessing this will land on a 'yellow vest protesters did it to frame muslims '
Also, who is walking along the upper balcony area in the live feed of the early fire? strange