Is it reasonable to say that in many (not all) parts of London, English no longer functions reliably as the default public language, even if most individuals technically "speak English"?
What this is, is a racist meme pretending that the significant fraction of immigrants to London who may occasionally speak their native language to each other in public is somehow a problem. Exactly equivalent to Americans panicking about Spanish.
Edit: Changed to link I like a bit more
Certain people would rather fearmonger though.
The net (and the UK has decades of experience in this, eg with the South Asian immigrants that arrived in the 1950s-1970s) is that while the first generation may only get to decent levels of English, their children are bilingual or monolingual in English, not monolingual in their ancestral tongue.
Occasionally you will get someone with a political axe to grind who visits an area with a lot of immigrants, doesnt hear a lot of English, and posits that there are ethnic monolingual enclaves where they cannot go. I think this is more likely to be a failure of understanding.
I was surprised the first time I got into volunteer work. Figured that these wives have never spoken English in their home country. So when they moved to London, they learnt English from scratch and picked up the local accent and speaking style. Their grammar may not be perfect sometimes but whose is?
As for its relevance: "native speakers on English", etc.
One of them is Kurt Caz.
(https://news.ycombinator.com/item?id=46809291)
You should watch the video someone linked that exposes one of his many shady stuff.
Absolutely false. My god! Have you even been to London? Stop consuming propaganda from Twitter/X and Facebook. It isn't good for your mental health.
I do not use Twitter nor Facebook. I watch YouTube videos. These YouTubers have >1M subscribers.
I see you have not been around in London for over 10 years. How was it back when you were in London? I've been in London for 10 years, so I probably came when you left. Never once I have been in any part of London where English was not the lingua franca. Yes, people speak their native languages too among themselves but I haven't met anyone anywhere in my 10 years who couldn't speak English. I don't think this is any different from any other megacity of the world.