App was installed from Fdroid, but I’m curious why it can browse any folders and see all files. Going into App settings, the Permissions is greyed out. Usually Android will prompt if I want an app to allow access to files (full/limited/none) but not for this app.
are you sure that it has that access?
on my phone the “select file to open” button just opens the system built in file browser, which is used to grant apps access to individual files or directories.