If SoftBank want to maximize their return then they'd probably do best to list ARM in the US. There's no way they'd get the crazy valuations you seen on NASDAQ on the LSE. It's why so many UK tech companies IPO in New York. They don't seem to get particularly excited about tech in London.
That's because a lot of these ""tech"" companies are just other business models in disguise. My especially favourite are the unsustainable business model food delivery apps like Deliveroo and JustEat, or the retail apps that are classed as tech for some reason like online consumer brands such as Victorian Plumbing and whisky seller Artisanal Spirits.
It's clear to me that IPO's are no longer about long term equity, and more about short term gambling. This is especially true when you have both US and UK markets actively trying to attract more retail investment, just to swindle the public out of more money. Until we see a radical shift in the way we think about and measure the performance of companies, IPO's and equity markets will continue to be a wild ride.
JustEat isn't unsustainable. They are profitable (pretty wildly so until they started offering their own delivery riders to grow to outlets which don't have drivers -- which has started hitting margins).