This generally should not be a problem. Unlike with banks, who hold your cash directly, brokers (including Freetrade) keep their clientsā assets segregated from their own pool of assets. This means that if Freetrade was to liquidate, you would simply transfer your portfolio to another broker.
To give you a comparison, when Lehman Brothers went into liquidation in 2008, all of its clientsā $275,000,000,000 of assets were transferred to other brokers, mostly Barclays who took over Lehmanās investment banking division. Customers did not take a hit. I do not see any reason for any UK broker to have a different approach.