My question was focussed on moving shares that are already tradable on Freetrade and that are not in an ISA or other tax wrapper.
E.g. for the US: Transferring Common Stock From One Broker to Another?
Probably depends on how and where the shares are registered, unless the process is to sell and re-buy, which I would doubt. An added complication is that the broker to move from could be outside UK.
Employee stock grants can also contain fractional shares because of taxation, but that shouldn’t be an issue with Freetrade after the rollout of fractional shares.