- Go to your Nextcloud account security settings using a browser. Create a new app password.
- Open Nautilus and select Connect to Server from the left sidebar.
substituting YOUR-DOMAIN.TLD/PATH and YOUR-USERNAME as needed. If your server is not using https, substitute davs:// with dav://. (Also, shame on you.)
- Enter your username and app password (created at step 1, above) when prompted.