Check the protocol on the remote end before you try installing another app. ‘Remote storage’ is a very broad category, and a NAS, an SFTP server, a WebDAV account and a cloud provider API may appear as a folder but the best way to replace them is different for each.
If this is your own NAS or server, try to avoid having to use a cloud-mounting software if you can, and instead use a private VPN (or similar) to connect to it and mount an SMB share with your OS’s file manager
This will both give applications a more traditional network filesystem to interact with, and will avoid having to add another potentially troublesome utility to your stack. Avoid exposing SMB shares to the internet.
For a hosted SFTP, WebDAV or cloud account, the choice is easier:
- Use Rclone if cost matters and you can tolerate configuring the mount yourself.
- Use CloudMounter if you want a GUI and separate mounted locations without maintaining scripts.
- Do not choose Cyberduck if the requirement is a drive visible to every application. It is a transfer client, which is a different workflow.
- On Windows, RaiDrive is worth considering, but check whether the account type and features you need are included in its current license.
There is no replacement that makes Internet storage behave precisely the same way as an internal SSD. You can not have both “offline access” when disconnected and “software does not store data on local machine”, unless you are willing to have applications show disconnections. These requirements are mutually exclusive, no matter how hard you try to convince yourself otherwise.
I would also not use package files or Thumbnails in Finder as a test sequence. Pick actual applications that will be using this mounted volume as their storage, not just some random data files. Adobe projects, photo catalogs, databases, virtual machines, and mail archives are generally a bad idea to keep in any remotely network-mounted storage. Keep these critical volumes local and synchronize them with the remote server. Regular documents, media, and archives are much less taxing on a network.
In addition to speed and reliability, you may want to consider credential management options. Does the replacement offer to store credentials in the credential manager, if one is available, or does it try to prompt you for them each time? Does it have a way to store SSH keys on the remote server, so you do not have to type them every other hour? Does it keep the connection alive when the system goes to sleep? A pretty icon in the menu bar is great and all, but it will do nothing if the connection dies at 3 AM.
For a direct replacement for Mountain Duck, CloudMounter offers the closest in terms of ease of use if you need something minimally maintained. If you want to retain absolute control over your data and not rely on a third-party service, rclone is the way to go. If your applications do not work reliably with any of these two, it may be best to abandon the search for a new Mounter and switch to a different workflow instead. Working locally and then syncing with the server is less elegant, but generally more dependable than trying to convince your applications that a remote server is their local disk.