If you've been to Kefalonia recently ...

[pallindroam]

... will we need to take any Euros in cash or is it nearly all contactless payments like here?

Not Kefalonia but, if it helps, on a similar Greek Island last year most places took card but there was one card machine failure/signal issue and the monastery we visited in dogs hills was cash only for refreshments and local produce.

So my advice is back up cash - enough to cover a meal or two plus a bit extra.

Everywhere we went took card, but I’d take £50 in Euros just in case