Most guitar riffs are based around single notes. There are only a few that use full chords. AC/DC have come up with plenty. But other than them, this is the only riff that comes to mind based entirely on chords.
Because it’s all chords, the riff works well on the uke. I’ve kept it in the original key of A. This means that the chord inversions are different – giving the riff a slightly different flavour on uke.
The strumming for bar three is down, up, up, down, down, up, up, down.