I’m facing exactly the same situation (images not shown in the dashboard but in frontend, no changes to config, fresh install).
Here are some informations for you:
Hosting Type: Shared Hosting
Package: Hosting Basic
Enabled PHP version: 7.2
If it’s helpful for you, I can PM you login credentials for the installation, or the domain name for debugging.
On my other webspaces/servers (IONOS, VPS server) this doesn’t happen.
Edit: Maybe it’s related to the glob function used in the filesystem core. On some systems (Solaris e.g.) the glob function doesn’t work as expected sometimes. I’ll create an additional instance and manually test it.