Who won the 2020 British Open?

No one. The R&A decided to cancel The Open in 2020 due to the Covid-19 pandemic.

More about the 2020 British Open cancellation

The British Open was due to be played in Kent from 12-19 July 2020 but it has been necessary to cancel the Championship based on guidance from the UK Government, the health authorities, public services and The R&A’s advisers.

This is the first time since the Second World War that golf’s original Championship, first played in 1860, has been cancelled.

Source: https://www.theopen.com/

British Open Winners