I used to mount network attached storage in /mnt until I had problems accessing it from a Snap. In searching for a solution it was pointed out that snaps are correct in being sandboxed from these types of folders, and users like myself are making things difficult for ourselves by using those system folders.
They said the best practice would be to mount them in a folder in your home directory. I've switched to doing that and it works great.
Oh cool, this looks like something I'd really like. I've been using a paid Android app called Simply Auto which is excellent, but self hosting is more fun.