TLDR: Overcome common permissions errors and missing graphical library issues when installing Dropbox on Fedora's immutable desktops (Kinoite/Silverblue) by running it inside a Distrobox container.

1. Flatpak attempt Initial install as a Flatpak. > running ok until "sign in" then Your Dropbox folder is on a file system that is no longer supported
2. Flatseal attempt Changed the file sharing settings under the Filesytem section. See https://universal-blue.discourse.group/t/your-dropbox-folder-is-on-a-file-system-that-is-no-longer-supported-solved/1112
3. OSTree / rpm-ostree attempt