I did not understand that point at all. The author writes: "The loss of this funding and scientific exchange is a major loss for British and European academia — and innovative companies who need to hire the best scientific and technical talent." But what is it exactly that the UK lost [funding-wise, science-wise] due to Brexit?
This isn't true, you don't have to be a member of the EU to be part of the Horizon programme, which is the EU's science funding mechanism. Membership of Horizon was part of the Brexit deal for the UK, although it seems to be uncertain now as part of the wider disputes.
Historically, Israeli computer scientists have been able to apply and win ERC grants. That said, I have not checked if anything has changed for the UK in this regard, hence why I am curious.
AFAIK, unless this changed British scientists can apply to Horizon Europe funding, which includes ERC grants. However, there is some uncertainty as this is related to the trade and cooperation agreement, which looks a bit shaky right now.
One of the problem was that the British government does not keep its word, so people are wary of putting British colleagues only for their funding to get pulled at the last minute because lord Frost wants to annoy the EU.