I had the same problem with keepassxc snap. The snap can not access the path of my other hard disc for storage which is mounted at /media/data
The solution is to install the snap in classic mode:
snap install --classic keepassxc
This allows the snap to access all system files. Until the snap developers create the required interface installing with --classic mode is the only solution i can see.
(An interface consists of a connection between a slot and a plug. The slot is the provider of the interface while the plug is the consumer, and a slot can support multiple plug connections.) Interface management