All files pokes a big hole, really you want portals. You probably also want audio. And perhaps graphics acceleration depending on the software, and other limite

All files pokes a big hole, really you want portals. You probably also want audio. And perhaps graphics acceleration depending on the software, and other limited hardware access. And dbus (but sandboxed proxy access). Probably some global config from the host as well (fonts, themes, cursor). And…well maybe there’s more but the point is it depends on the software. Maybe it is that simply sometimes. Often it’s not for non-trivial applications.