It is not possible to switch between proton accounts on an Android phone for the Calendar and Drive app products. I use one account for personal email and another account for business email. So I must put all my calendar events in one account. Also, when I need to save things to Drive, I must save them all to one account, then later download some of those things to my computer, delete them from Drive, and upload them to the other account. This can be a burden. Thanks