Note that this is actually a problem with the fuse3 package: it provides the fusermount binary without accepting the -o nonempty mount option. fuse3 must not provide fusermount, only fusermount3.
(I am not re-assigning this bug since the problem can also be worked around in S3QL, and IIRC there already is a bug filed against fuse3). -- GPG Fingerprint: ED31 791B 2C5C 1613 AF38 8B8A D113 FCAC 3C4E 599F »Time flies like an arrow, fruit flies like a Banana.«