Pier

Pier turns a remote folder into a normal Windows drive letter. It speaks WebDAV (Nextcloud, ownCloud, Synology, QNAP, Apache, IIS), SFTP (any SSH server, password or OpenSSH keys) and NFSv3, and uses the open-source Dokany driver, installed for you by the setup program, so Explorer, Office, backup tools and scripts work on the drive as on a local disk.
A WebDAV drive is one link: paste the address (for Nextcloud, the WebDAV link from its settings) and only the password is left to type. The interface speaks 16 languages.
Built for slow links and big files: files are fetched in blocks into a cache on your disk, so only the parts you touch are transferred and nothing is downloaded twice. Uploads and downloads that break resume from the last block; a dropped Wi-Fi, a VPN reconnect or a sleeping laptop does not lose the drive. A drive can be switched to offline mode and keep working from the cache; changes are pushed later.
Pier Backup makes encrypted, versioned backups of your folders to WebDAV, SFTP, S3 or NFS: only changes are sent, any version can be restored.
Pier runs as a Windows service, so drive letters exist for every user and survive reboots; a tray icon gives mount, unmount, sync and "open in Explorer", and a command line covers scripting.
Free edition: up to 5 drives, all protocols and features, no time limit. Pro: unlimited drives and no ads, USD 19 per year.
Requirements: Windows 10/11 64-bit or Windows Server 2019+.