I finally had time to try this, but support for mount_options.conf was added to udisks2 in version 2.9.0. Sadly the Linux distribution I'm using for audio stuff is still Ubuntu 20.04 which ships with udisks2 version 2.8.4.

So I manually remounted the loop device using mount -o remount,unhide /mountpoint and now I'm seeing the hidden files.

Again, thank you very much for your guide! :)

Happy it helped you! Thanks for the feedback! Wish you an enjoyable journey~