I tried running sheltered from the f-droid repository with it not really working that well; refusing to show notifications during setup. I'm not sure of this is because it hasn't been updated in the last 12 months, or if its something on my end.
Any help is appreciated.
Android has built-in support for a so-called "work profile", so folks can use their personally owned smartphone for work tasks with reasonable isolation. It has a separate file system, separate apps list, separate contacts etc…
Normally, this work profile will be activated and managed by your employer. Shelter (and similar apps, e.g. Insular) allows you to activate the work profile yourself and do basic management, like copying apps and files into there.
From a privacy viewpoint, it's great, if you're e.g. forced to use WhatsApp, but don't want it scraping your contacts.