@keneda I do not have a complete solution for everyone, just what I did:
export LD_PRELOAD=
(libtls-padding.so
causes unexpected things)- boostrap chroot filesystem as per https://wiki.debian.org/Debootstrap
- mount /proc and /sys, bind mount /run/dbus (optional for smbnetfs) and /dev (fuse there)
- chroot in with 3003 (and optionally 3004) supplementary groups
- add apt_ user to 3003 (and probably 3004) groups
- edit /etc/resolv.conf with nameserver of preference
- install smbnetfs with apt-get, configure as per https://wiki.gentoo.org/wiki/Smbnetfs (I only needed auth line)
- mount smbfs in chrooted environment with allow_others option
- on a host filesystem as a phablet user create a symlink under Downloads (any folder accessible by filemanager without unlocking is fine) to the required share(s)