Hi, gocryptfs author here, upstream ticket:
https://github.com/rfjakob/gocryptfs/issues/892

Debian currently ships a combination of gocryptfs and
https://packages.debian.org/bookworm/golang-golang-x-sys-dev that
results in "Operation not permitted" errors under the following
conditions:
1) Mounted as root
2) -allow_other is set

Root cause is https://github.com/golang/sys/commit/d0df966e6959f00dc1c74363e537872647352d51
which changed unix.Setreuid to affect the whole process instead of
just the current thread.

Upstream now has their own Setreuid (
https://github.com/rfjakob/gocryptfs/commit/6b1ba5846b17eec710a70cb6c6bf23e3f2024289
).

Would be nice to get this into Debian, but it's a few patches and a lot of LOC.