Since last week, Dropbox (installed from flathub) was refusing to work in my Fedora Silverblue 29, even having my home partition formatted as ext4.
The error was:
Can't sync Dropbox until you sign in and move it to a supported file system
Today I found the solution: my home partition is mounted at /var/home and I have a /home symlink pointing at it. Apparently Dropbox didn’t like that. The solution was to tell Dropbox to use the folder /var/home/jorge/Dropbox
Talking with the maintainer of the Dropbox flatpak in this issue he told me that in Endless OS it works fine. The reason could be that they set $HOME to
/sysroot/home/$USER instead of
/home/$USER as I think Silverblue does.