Fuse 3.17.+: Locking vault fails

## Summary

Updating the flatpak to libfuse version 3.17.+, once opened vaults cannot be locked anymore.

## Description
We regularly check for new libfuse versions (e.g. https://github.com/flathub/org.cryptomator.Cryptomator/pull/121).

Unfortunately, all patch versions cannot be used by the flatpak, because locking via fusermount3 fails. There is a discussion for possible reasons, see https://github.com/libfuse/libfuse/discussions/1323. But yet, there is no resolution.

Start by reproducing the locking failure in the Flatpak after updating libfuse to 3.17.+, then read the linked libfuse discussion and flathub PR 121 for context. Done means identifying a resolved compatibility path for fusermount3 or documenting that no usable libfuse 3.17.+ version is available.

Written by the indexing model from the issue text.