That's exactly why you want to do this. When people speak casually or are making jokes, nobody speaks with grammar in mind. Gathering this intuition for the language is exactly what I'm looking for when learning.

And a lot of native speakers just straight up use incorrect grammar. eg loads of native English speakers say things like "could of", use "then" instead of "than", use punctuation incorrectly, do incorrect sentence structure, etc.

I don't mean to be prescriptive about language. Of course it evolves based on usage. But in any formal environment, such as an academic environment, there are still certain defined and canonised English grammar rules that you would be penalised for breaking, and most learners want to learn those rules even if most casual speakers don't follow them.

You just look for people who are interested to learn your language, any place where people communicate can work. Maybe hit some groups for learning the language you know and try to find people who speak the language you want there.

I personally play VRChat, there are a number of language learning groups there. Though, the culture of the place is certainly not for everyone.

I used to use HelloTalk but it's a bit annoying now due to trying to lock more things behind paywalls. Italki is another common one. Just find any language learning/exchange discord, like TheMoeWay and others.

I saw a few days ago this really cool guide to language exchanges on YouTube.