"as many have noted", I suppose.

I'm always baffled at how many people write "of" instead of "have", they don't even sound the same

The classic one is "should have" or "should've" to "should of" because when spoken, it really does sound similar. I don't know what the fuck people are learning in English classes these days though, or if they even still have them.

They sound exactly the same to me.

Wiktionary gives <should've> as /ˈʃʊdəv/, unstressed <have> as /(h)əv/ and unstressed <of> as /əv/.

one is v the other is f

Spelling is no guide for pronunciation here, though. In North American and Commonwealth dialects of English I don't think there's a context in which the <f> in <of> is really pronounced as a [f]. It is rather a [v].

Only in South Asian varieties of English apparently: https://en.wiktionary.org/wiki/of#Pronunciation

Not sure where you're from but in my dialect (North American) it's more common than not to have _have_ realized as [əv] ("uhv") in contexts like _should have_, _could have_ (but not _I have a car_, where it has to be the full [hæv]). Only in deliberately enunciated speech do I feel like I'd expect [hæv] in the former kind of context. So it's an understandable mistake to make.

I'm a French speaker, not an English speaker.

Which might actually make me less likely to make certain mistakes, precisely because I'm not influenced by pronunciation, only by grammar (I actually have to think about the words I use)