There is also a problem where snapd fails if your home directory isn't called /home/username (i.e. if it's located in a different path).
At this point snap sounds like a bad joke to me. Especially when Flatpak already exists.
https://bugs.launchpad.net/ubuntu/+source/snapd/+bug/1662552
Yup. There needs to be considerable work to integrate snaps from completely sandboxed (no access to file system/network/hardware), to giving them controlled access to some resources, managed/monitored by root and/or user.
The limitation stems from a design problem, details at https://bugs.launchpad.net/ubuntu/+source/snapd/+bug/1643706.