You can see all the scrappage schemes manufacturers are currently running here: www.honestjohn.co.uk/news/car-market-1/2020-06/you...#

I've checked on Citroen and Dacia's sites and can't see any stipulation requiring the trade-in car to have an MoT (seeing as it's being scrapped anyway) but it should say in the fine print on each site. If you're not sure, and you're interested in a particular scheme - I'd ring up your local dealer and ask them what the conditions are as they're likely to be slightly different for each manufacturer.