Theres a lot more to the android app sandbox than just running processes as seperate users. Theoretically something similar could be implemented in some other 'typical linux system'. It would be a huge undertaking. If you are thinking about security need to consider not only malicious apps, but possible attack vectors opened up by any application. This paper is a couple of years old, it explains how it all works on Android https://arxiv.org/abs/1904.05572