And the "wave" was a handful of unrelated fires that happened near churches (not even in churches for most of them) over a few years and were mounted as a "wave of arson" by extreme-right websites during the height of Syrian refugees influx.

The original website that had a map of these events (that you had to look up yourself to see they amounted to nothing) isn't even online anymore as far as I can see, now this false fact is just a urban legend with a life of its own.

I've seen news of churches (Catholic, as most Churches are in France) been set on fire maybe 2 or 3 times in the news here in France, that was a while ago... Not seen any news like that recently. Are there any sources about the true numbers of these arson fires ?

I had the same conversation with someone living in the US at the time of the Notre-Dame fire, I couldn't come with more than 2 or 3 occurrences reported in the French press naming specifics cases with places names and all, while he, in the US would provide me with dozen of press reports of "Churches are burnings by numbers in France !" type of titles ... Many from a very specific side of the political spectrum.