Here is a good article on Scale AI an Appen competitor https://www.notboring.co/p/scale-rational-in-the-fullness-of.
It made me more bullish on data labelling/AI as a business model long term as every company will need to use AI in future but won't have the internal resources. But it doesn't bode well for Appen that revenues are dropping (while Scale AI is doubling revs) and they are having to do acquisitions rather than build the tech internally.