In most languages, the letter R is trilled or rolled. Not so in English.
So how do other languages hear and describe our ‘R’? And while we’re at it, are there any other languages that don’t roll their R like we do? (I suspect German may. But I am not even sure about that.)
I’ve seen francophone references to “the dog’s growl” in english.
You will want to look at the “Postalveolar” table on this page:
~Max
It talks about the English “r” and then compares it to other languages.
This seems like a general question (factual) more than an opinion-based question. I’m moving it there.
Were they really talking about English, and not the “r grasseyé” which occurs in French (e.g., in Paris), compared to a rolled r?
Francophones in Quebec; I understood them to be referring to what English sounded like.
Ben Jonson called the English r “the dog’s letter” in his English Grammar of 1640.
As I recall, the conversation also touched on the “th” sound in English, which some francophones find difficult. It was a conversation about difficult English sounds.
On the other hand, I’ve also seen francophones wince at some anglos with a strong English “r” speaking French. I’ve heard it called “the Diefenbaker accent”.
The most notable time I remember was a future Governor General with a strong English accent, including the “r”. Some of the francophones in the audience thought it just would have been more respectful for him to speak English and leave it to the translators. 
Fun fact: Few of the world’s six-thousand-plus languages have this particular kind of rhotic, but by coincidence the two biggest languages do have it: English and Mandarin Chinese.
They do? How the hell does that substitution work?
I must have had a brain cramp when I wrote that. It makes no sense. What the French Canadians and the French do is typically substitute their own r for the English. Except a great many French Canadians learned English at an early enough age to speak English perfectly (which the present government is trying its damnedest to prevent).
The quotation from Larousse concerned what the french do with the th, another sound rare in natural languages. French Canadians join Brooklyners is using a d for that sound. That Brooklyn dialect is dying out. My grandson who has lived in Brooklyn his entire life has none of it.
Which? The voiced, as in “that”, or the unvoiced, as in “thin”?
Both.