LeOS is created to get the most privacy for the users. I have removed a lot of google code form sources. Installing any spying app from google or facebook like gmail or WhatsApp is stupid on such GSI, because it breaks you privacy and you will lost all your private data and the big player can sell your data. If you need any google apps use them in browser. Gapps are including google play services. They won't work on LeOS. As written before, MicroG is a FOSS replacement for goolge play services. But not ll apps will accept this replacement.