@guerda
Ich nutze den cxFileExplorer und bin sehr zufrieden.

(Medien: 1)

@guerda
I use Material Files and Amaze File Manager.

For some definitions of simple, there's also andSMB. But I don't know how up-to-date that app is...

@guerda my corresponding app list at https://android.izzysoft.de/applists/category/named/network_admin_mount names an app called "CIFS Document Provider" (https://f-droid.org/packages/com.wa2c.android.cifsdocumentsprovider/) to mount Samba drives so all apps can access them transparently. If I'm not mistaken, CIFS can be said to be a synonym to Sambe, in a way, right?

From the app's description: "Supports SMB, FTP, FTPS and SFTP." – so it should fit your needs. As the second link shows, the app is available at @fdroidorg